This has yielded some odd results. If you open CustomTessellation.cginc, you will note that it has already defined vertexInput and vertexOutput structs, as well as a vertex shader. To ensure the normal is facing the correct direction, we make use of the optional VFACE parameter we have included in the fragment shader. Send me some feedback about the tutorial in the form below. We can now add the hull and domain shaders to our grass shader. It would certainly be less redundant to take in a point as our input. Use Unity to build high-quality 3D and 2D games, deploy them across mobile, desktop, VR/AR, consoles or the Web, and connect with loyal and enthusiastic players and customers. a) maxvertexcount indicates the max number of vertices that might come out of this geometry shader, including new vertices you created during this phase or deleted vertices. We'll modify our code to reflect this. The rotation can be applied to the blade by multiplying it with the existing tangentToLocal matrix. HDRP however, supports “double-sided” out of the box, you just need to turn it on. Embed. A grass texture included as part of Unity's, mul(mul(mul(tangentToLocal, windRotation), facingRotationMatrix), bendRotationMatrix), GenerateGrassVertex(pos, width, 0, float2(0, 0), transformationMatrixFacing), GenerateGrassVertex(pos, -width, 0, float2(1, 0), transformationMatrixFacing), GenerateGrassVertex(pos, 0, height, float2(0.5, 1), transformationMatrix). I am a game design and cs student at NYU. We will use these two channels as the X and Y directions of the wind. Our goal is to allow the artist to define two colors—a top and a bottom—and interpolate between these two colors from the tip of the blade to the base. What would you like to do? a point or a triangle. To resolve this, we will construct our grass blades in tangent space. The latter function works the same way as the Quaternion.AngleAxis C# function (although AngleAxis3x3 returns a matrix, not a quaternion). To do this, we'll need to construct a rotation matrix that rotates a random amount around the blade's up axis. By taking t to a power, its influence on the forward offset will be non-linear, shaping the blade of grass into a curve. We will correct this by instead constructing our blades with several triangles and bending them along a curve. We will use a Unity macro for this, and include it in an #if statement to ensure the operation is only run during the shadow pass. In actuality, a triangle is being drawn for each vertex in our mesh, but the positions we are assigning to the triangle's vertices are constant—they do not change for each input vertex— placing all the triangles atop one another. We will also add some simple illumination, received from the main directional light. inout keyword serves that functionality: since we are processing on triangle basis, we need a structure to output them; Therefore we need this stream object. This tells the GPU that we will emit (but are not required to) at most 3 vertices. Note the line declaring float3x3 transformMatrix—here we select between our two transformation matrices, taking transformationMatrixFacing for the vertices at the base, and transformationMatrix for all others. This texture will be similar to a normal map, except with only two channels (red and green) instead of three. Even when multisample anti-aliasing (MSAA) is enabled, Unity does not apply anti-aliasing to the scene's depth texture, which is used when constructing the screen-space shadow map. Geometry shader, in ShaderLab term, is actually a method in Unity shader program. Other than having a new fragment shader, there are a couple key differences in this pass. First, geometry shader is in a form of a function in Unity, we need to tell the compiler that we want to program a geometry shader. There must be a way with just shaders. One solution would be to create a new, denser mesh, either through C# or using 3D modelling software. A further discussion on this topic can be found here. Right now, the vertices in our blades of grass do not have any normals assigned. Right now, the triangles are all being emitted in the same direction, rather than outwards from the surface of the sphere. This pass will be used by shadow casting lights in the scene to render the grass's depth to their shadow map. Fortunately now the programmable pipeline is way more flexible than in 2005. We will correct this by updating our output vertex positions to be offsets from the input point. Geometry Shaderの書き方; Unity Graphics Programming vol.1; Unityシェーダープログラミングの教科書 ShaderLab言語解説編 ; Unity Shader Programming Vol.01 (v.2.0.0) StandardGeometryShader; Edit request. Add the following below the line declaring float width. Triangles are now correctly drawn with their base positioned at their emitting vertex. To calculate the forward offset of each vertex, we will plug t into the pow function. These tutorials are made possible, and kept free and open source, by your support. The UV coordinates of the three vertices of our grass blades. Download shader: We can access a right and up vector by adding some new vertex inputs. Unity will automatically increase the target to this level if it was defined lower, but let's be explicit about it. [maxvertexcount( NumVerts )] void ShaderName ( PrimitiveType DataType Name [ NumElements ] , inout StreamOutputObject ); To do that, simply add the following after vertex and fragment shader declaration: Second, we need to know geometry shader processes data passed from vertex shader and past them to the next stage, fragment shader. Geometry Shader; Pixel Shader; Tesselation Shader; Fragment Shader; Unity helps you when using shaders. If we enable the TessellationExample object in the scene, we can see it already has a material applied that implements tessellation. Uses a geometry shader to generate blades of grass. Code placed in this block will be automatically included in any passes in the shader; this will be useful later, as our shader will have multiple passes. Before we do this, it will be useful to move some of our code calculating our grass vertex positions into a function, as we will be using the code several times in and outside our loop. While this would work, it would not allow for dynamic control of the grass density. Each segment will be rectangular in shape, and made up of two triangles, excluding the top segment—this will be a single triangle representing the blade's tip. This may be desirable for well tended grass, like on a putting green, but does not accurately represent grass in the wild. We'll add some curvature to the blade by offsetting the Y position of the vertices. But we can still play around with the geometry shader to create other interesting effects like rectangle extrusions, etc. triStream.Append(GenerateGrassVertex(pos, width, 0, float2(0, 0), transformationMatrixFacing)); The geometry shader can then transform these vertices as it sees fit before sending them to the next shader stage. This means our geometry shader will need to also run in the shadow pass to ensure the grass blades exist to cast shadows. This way, every blade will get a different rotation, but it will be consistent between frames. Zooming in, we can see some artifacts on the surface of the blades; this is caused by individual blades casting shadows on themselves. creative coder. Follow. The shader file has two functions included that will help us do this: rand, which generates a random number from a 3-dimensional input, and AngleAxis3x3, which takes an angle (in radians) and returns a matrix rotating that amount around the provided axis. We will implement wind by sampling a distortion texture. c) TriangleStream is a little bit tricky. This article will not go into implementing tessellation in detail—instead, we will make use of the included CustomTessellation.cginc file. With these vectors, we can construct a matrix to rotate our blade of grass from tangent to local space. We will add some properties to control this, as well as some properties to add some random variation. This could be adapted to work with grass; instead of drawing ripples where the character is, the blades of grass could be rotated downward to simulate the footstep impacts. Take a detailed look, and you will find that this pyramid actually consists of two separate triangles. Tessellation is an optional stage in the rendering pipeline that occurs after the vertex shader, and before the geometry shader (if there is one). The core takeaway from this is that geometry shaders are the step between vertex shaders and fragment shaders, and this is a concept you’ll keep seeing in the shader examples too. To extend this shader to cover vast, open fields, some optimizations would likely be necessary to keep it performant. 首先要知道，Geometry Shader和Vertex Shader以及Fragment Shader的区别。. Change ). Geometry shaders take in a single primitive as input, and can generate zero, one, or many primitives. To do this, we will add a preprocessor directive to the ForwardBase pass to compile all necessary shader variants. If we retrieve the source for this macro from Autolight.cginc, we can see it requires the shadow coordinate to have a specific name. Now we have successfully created a pyramid-like extrusion shaders. A geometry-shader object processes entire primitives. Because our shader has Cull set to Off, both sides of the blade of grass are rendered. 不过也是因为Unity的开发者大多数面向的是移动平台开发，所以Geometry Shader作为DirectX 10的特性并没有被开发者广泛使用。. … The tangentNormal, defined as directly backwards on the Y axis, is transformed by the same matrix we used to convert our tangent points to local space. As a final step to complete this shader, we will add the ability to cast and receive shadows. 28. genki toyama @genkitoyama. Therefore, when the anti-aliased scene samples the non-anti-aliased shadow map, artifacts occur. As well, we will use the built-in shader variable _Time to scroll the wind texture along our grass surface. We will begin by writing a geometry shader to generate triangles from each vertex on our mesh's surface. To sample this texture, we'll need to calculate the screen space positions of our vertices, and pass them into the fragment shader. This space is called tangent space. Add the following to the CGINCLUDE block. I'm working on trying to create a cg shader that emits a quad from each vertex of a mesh. So as we process each triangle, we need to first find the longer side of the triangle and consider this as the central side because in this way we can extrude our pyramid tip from the middle point of this lateral side: Now we just need to construct three triangles, namely ABC, ACD, and ABD. We can now visualize the normals in our ForwardBase fragment shader to verify our work. We'll create a new matrix to rotate the grass along its X axis, and a property to control this rotation. These can be organized as individual variables or as part of an interface block. It is unnecessary to redefine them in our grass shader; they can be removed. Note that even though this is a setting in the graph matter node, you need to turn this on in the material. We first need to find the direction by which we extrude the point A. You'll notice that these functions, along with the vertex shader, are enclosed in a CGINCLUDE block placed outside the SubShader. Like any kind of space, we can define the tangent space of our vertex with three vectors: a right, forward, and up. Geometry shader, in ShaderLab term, is actually a method in Unity shader program. Instead, we will subdivide the input mesh using tessellation. We will multiply each vertex in our blade of grass by this matrix before it is passed into UnityObjectToClipPos, which expects a vertex in local space. Line 10 indicates that the albedoof the material, that is its base colour, should be white. The fixed facing argument will return a positive number if we are viewing the front of the surface, and a negative if we are viewing the back. Their main purpose is to get the information from the separate vertices via the vertex shader, assemble the primitives that will form the object (usually it’s going to be triangles) and send the final … To sample them correctly, we will need to provide the fragment shader with UV coordinates. When a geometry shader is active, it is invoked once for every primitive passed down or generated earlier in the pipeline. One solution is to use anti-aliasing applied during post processing, which is available in Unity's post processing package. View all posts by jingyuLiu. Although we will color our blades with a simple gradient, laying the coordinates out in this way could allow for texture mapping. As a first pass on our solution, we'll calculate the normal assuming no curvature. The subdivided blade of grass represented as a triangle strip, constructed one vertex at a time. b) This method accepts an input of type v2g, regards it as a triangle (since we know that models are made of triangle primitives), and names it as input whose [] operator would give access to the three vertices of the triangle. Note that the return type of this function is void, so that we need another way to pass our modified data to the next stage. We can now construct a matrix to rotate about this vector, and multiply it into our transformationMatrix. Unity is the ultimate game development platform. Note that we rescale the sampled value from the texture from a 0...1 range to be in a -1...1 range. We can now add GenerateGrassVertex calls to our loop to add the vertices to the triangle stream. An example: That's a prism in a huge white box-shaped room. We declare a loop that will run once for each segment in the blade. Unityで100万個のキューブ（立方体）を表示を行うと、どうしてもパフォーマンス問題にいきあたる、Unityでは計算量が多くなるとShaderを書く機会が多くなるが本 GeometryShader では任意の座標にキューブを描画する Shaderを書いてみました。 Modifying the Tessellation Uniform property now allows us to control the grass density. The heart of a surface shader is its surface function. Each … Even though in other game engines, geometry shader might itself serve as a small program, Unity3D conveniently combines vertex, geometry and fragment shaders into a hodgepodge which maintains its structure by ShaderLab syntax. Our geometry shader doesn't yet do anything; add the following code inside the geometry shader to emit a triangle. First we construct three side triangles we just talked about. We use the position again as our random seed, this time swizzling it to create a unique seed. While this is permitted in DirectX HLSL, it is not permitted in OpenGL, and will generate an error. Then we declare a variable called _Factor that describes the intensity of the stretching: Now we start to construct triangles using left-handed coordinates (clockwise). However, sometimes post-processed anti-aliasing is not always appropriate (such as when working with virtual reality); this thread on the Unity forums has a good discussion for alternative solutions to this problem. Taking in a position, width, and height, it correctly transforms the vertex by the provided matrix, and assigns it a UV coordinate. We'll use a #define statement to allow the shader's author to control the number of segments, and calculate the number of outputted vertices from that. We use the input position pos as the random seed for our rotation. Just like the vertex shader, you can move vertices around in a geometry shader. We will not implement specular lighting in this tutorial. This could be done as follows. We'll create a second pass that will make use of all of the same shaders as our initial pass, with the exception of the fragment shader—we'll define a new one that is populated with a macro that handles the output for us. Other entries in the Create > Shader menu create barebone shaders or other types, for example a basic surface shader. Geometry shaders take a primitive as input; each primitive is composed of some number of vertices, as defined by the input primitive type in the shader. By … As we move up the blade, the height increases, and the width decreases (as it tapers inwards). In order to cast shadows in Unity, a second pass must be added to the shader. I'll get back to you as soon as I can! After applying linear shadow bias, banding artifacts are removed from the surface of the triangles. 在DirectX 9的渲染管线中，可编程的Shader只有顶点着色器和片段着色器两类。. We'll make that change now. 2. Since our geometry shader is written inside CGINCLUDE blocks, it is available for us to use in any passes in the file. As we want our grass to be generated correctly for all kinds of surfaces, it is important to test it on different shaped meshes. If Unity cannot find a SubShader in the body of the shader that can render the geometry correctly, it rolls back to another shader that is defined after the Fallback statement. Well, because Unity tries to help in every way the development by providing libraries already prepared to avoid writing too much code by repeating the same functions. ( Log Out /  Why this difference? Can cast and receive shadows. This matrix will not include the windRotation or bendRotationMatrix matrices, ensuring the base of the blade stays attached to its surface. Many of Unity's built-in shader macros make assumptions about the names of certain fields in the various shader structures (some even make assumptions about the names of the structures themselves). Lower values of _BladeForward and _BladeCurve will result in a more organized, well tended field of grass, while larger values will have the opposite effect. Note that matrix multiplication is not commutative; the order of the operands does matter. If you enjoy them, please consider becoming my patron through Patreon. All gists Back to GitHub. We apply the _WindDistortionMap scale and offset to our position, and then further offset it by _Time.y, scaled by _WindFrequency. We can correct this by applying linear bias, or translating the clip space positions of the vertices slightly away from the screen. Ask Question Asked 3 years ago. We will start by adding a gradient that runs from the top of the blade to the bottom. Panning the camera around reveals that the triangle is being rendered in screen space. In this tutorial, the grass covers a small 10x10 area. Geometry shaders wo r k by procedurally generating vertices on the GPU side before sending them to the fragment shader to fill in. The outputs of the vertex shader (or Tessellation Stage, as appropriate) are thus fed to the GS as arrays of variables. We need to consider the structure a little bit: There are three important things we need to look at: Open the Main scene, and open the Grass shader in your preferred code editor. And that should be the normal of this triangle, which can be calculated using a cross product of two sides. We will deliver articles that match you. The first, triangle float4 IN[3], states that we will take in a single triangle (composed of three points) as our input. Please leave any comments! Why not register and get more from Qiita? The shader will take an input mesh, and from each vertex on the mesh generate a blade of grass using a geometry shader. Its job is to subdivide a a single input surface into a many primitives. Geometry shaders are an optional part of the rendering pipeline. This function carries the same responsibilities as our the arguments we currently pass in to VertexOutput to generate our blade vertices. However, because our input mesh (in this case, GrassPlane10x10 found in the Mesh folder) has a triangle mesh topology, this would cause a mismatch between the input mesh topology and our requested input primitive. While this is not a problem at long distances, up close the blades look overly rigid and geometric, rather than organic and alive. The grass will be capable of both casting and receiving shadows. If the grass isn't animating in the Scene view, click the Toggle skybox, fog, and various other effects button to enable animated materials. Following shows the final rendered image, and I'll describe the details in below. Alternatively, this could be resolved by using meshes with the Points topology type as the input mesh for our geometry shader. To make our triangles look more like blades of grass, we'll need to add some color and variety. As well, at further distances, instead of drawing each blade individually, clumps of grass could be drawn using a single quad that is texture mapped. We'll also make a single call to GenerateGrassVertex outside of the loop to add the vertex at the tip. After the initial three vertices, each additional vertex forms a new triangle with the previous two vertices. Use the following syntax to declare a geometry-shader object. triStream.Append(GenerateGrassVertex(pos, -width, 0, float2(1, 0), transformationMatrixFacing)); Our triangle is now correctly rendered in the world. Ideally, we want to build our blades of grass—applying random widths, heights, curvature, rotation—without having to consider the angle of the surface the blade is being emitted from. An example of how to do this with water can be found here. This value is in the 0...1 range, where 0 is fully shadowed, and 1 fully illuminated. But it is not definite. A geometry shader takes as input a set of vertices that form a single primitive e.g. So as we know, we used to use a struct called v2f to carry data we need from vertex to fragment shader. Each blade of grass will be subdivided into a number of segments. Embed Embed this gist in your website. Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. However, it appears that only one is being created. GitHub Gist: instantly share code, notes, and snippets. The blade's base is no longer pinned to the ground; it is intersecting the ground (in. Without interaction, graphical effects can feel static or hollow to players. Next, we can construct a normalized vector representing the direction of the wind. If we wished to have multiple triangle strips, we could call the RestartStrip function on the TriangleStream. At this stage, those vertices are … After we finish one point, we append it to the triangleStream. Now since we have an extra middle stage, we need to rename this struct and add another struct as well: (Note that in this specific shader, we want to directly pass object space coordinate to geometry shader because it is easier for later calculation. When the Blade Curvature Amount is set to 1, the blades of grass all face the same direction in tangent space: directly backwards on the Y axis. Instead of importing these binormals, Unity simply grabs each binormal's direction and assigns it to the tangent's w coordinate. If we wanted to have a different name for our coordinate, or we were required to for any reason, we could simply copy the above definition into our own shader. Rather than using texture coordinates assigned to the mesh, we will use the input point's position. Share Copy sharable link … I've found that a value of 5 produces good results. Change ), You are commenting using your Google account. A macro we use below, SHADOW_ATTENUATION, is no different. This tutorial will describe step-by-step how to write a grass shader for Unity. To create variation and add a more natural look, we'll next make every blade of grass face a random direction. As this tutorial is already very long, I abstained from including a section about how to have objects in the world interact with and influence the grass. In our example, the SubShader is the Diffuse built-in shader. Right now, our individual blades of grass are defined by a single triangle. We'll update our existing code with this function to ensure it is properly working. To create interest and realism, the blades will have randomized dimensions and rotations, and be affected by wind. Before moving on, set the GrassPlane object inactive in the scene, and set the GrassBall object active. Grass Geometry Shader for Unity. We also multiply UNITY_PI by 0.5; this gives us a random range of 0...90 degrees. Use the following syntax to declare a geometry-shader object. World of Zero (Tutorial by World of Zero) where he codes a geometry shader for a point cloud grass generator. Finally, in the fragment shader, we just use the texture coordinates passed from geometry shader to sample our main texture and output its color. While we could emit a blade from all three input points, this would cause neighbouring triangles to redundantly emit blades atop one another. As well, set the Tiling of the texture to 0.01, 0.01. To actually use a geometry shader, we have to add the #pragma geometry directive, just like for the vertex and fragment functions. ( Log Out /  Stock. The surface of the prism is just rendering the skybox of the scene (a starry sky). This way, if there are multiple grass meshes in the world, this will create the illusion they are all part of the same wind system. 【Unity】Geometry Shader（ジオメトリシェーダー）の超入門サンプル【初心者向け】 2019年6月16日 2019年7月3日. You can alternatively message me through Twitter or Reddit. ( Log Out /  Any shader not explicitly setting a function entry poin… Wireframe Geometry Shader Unity. 但是在DirectX 10开始，渲染管线增加了一 … What makes the geometry shader interesting is that it is able to convert the original primitive (set of vertices) to completely different primitives, possibly … The concept of Unity for surface shaders, for example, includes many … Founded some mesh wireframe shader in the unity 5.5f2 builtin shader folder (builtin_shaders-5.5.0f2\DefaultResourcesExtra\VR\Shaders).. Changes: – Added fillcolor, outline color – Added [x] Discard option (draws only lines) – Removed stereo rendering keywords – Removed color by distance thing. The grass blades' dimensions right now are fixed at 1 unit wide, 1 unit tall. The geometry shader sees two triangles, each with three vertices. This is an example that shows how to implement a geometry shader that is compatible with the standard lighting model in Unity. Set the Fence game object to be active in the scene; this gives us a surface for the blades to cast shadows onto. For improving on or extending the lighting and shading, while it is not natively possible to use geometry shaders with surface shaders, if it's desirable to use Unity's standard lighting model, this GitHub repository demonstrates a workaround by using deferred rendering and manually filling the G-Buffers. Once again, we apply this matrix through rotation, taking care to add it in the correct order. The second, of type TriangleStream, sets up our shader to output a stream of triangles, with each vertex using the geometryOutput structure to carry its data. Change ), You are commenting using your Twitter account. By default, Unity compiles shaders into almost the lowest supported target (“2.5”); in between DirectX shader models 2.0 and 3.0. To control the density of the grass, tessellation will be used to subdivide the input mesh. This is often called the DRY principle, or don't repeat yourself. Note that in this diagram, the fragment shader is referred to as the. We can now sample our top and bottom colors in the fragment shader using the UV, and interpolate between them using lerp. To complete this tutorial, you will need a working knowledge of Unity engine, and an intermediate understanding of shader syntax and functionality. Receive and cast shadows (custom GEOMETRY Grass Shader) - Unity C#. Viewed 4k times 1. We can now pass this through to the VertexOutput function, and then to the geometryOutput structure. Thanks for reading. However, as we are not using surface shaders, it is necessary to implement custom hull and domain shaders. We construct the UVs for our blade in a triangle shape, with the two base vertices at the bottom left and right, and the tip vertex placed center-top. triStream.Append(GenerateGrassVertex(pos, 0, height, float2(0.5, 1), transformationMatrix)); return lerp(_BottomColor, _TopColor, i.uv.y). This is not only more memory efficient, but also makes it easy to quickly construct sequences of triangles in code. Now we need to think about how we can construct the pyramid. This is a simple geometry shader written in CG language in Unity3D editor. With all three vectors, we can construct a matrix to transform between tangent and local space. ). The surface function doesn’t use any data from the original 3D model; d… In the ForwardBase pass's fragment shader, we can use a macro to retrieve a float value representing whether the surface is in shadows or not. For a more detailed look at implementing custom lighting in shaders, I would recommend taking a look at my toon shader tutorial. Note that the vertex shader vert in CustomTessellation.cginc simply passes the input directly through to the tessellation stage; the job of creating the vertexOutput struct is taken care of by the tessVert function, called inside the domain shader. Each iteration of the loop will add two vertices: a left and a right. Change ), You are commenting using your Facebook account. Tessellation is implemented with two programmable stages: the hull and domain shaders. When a mesh is exported from a 3D modelling package, it usually has the binormals (also called the bitangents) already stored in the mesh data. Great tutorial but I am wondering (and didn't find a proper … The above is a large chunk of code, but all of the work done is similar to what was done for the width and height of the blade. Even though in other game engines, geometry shader might itself serve as a small program, Unity3D conveniently combines vertex, geometry and fragment shaders into a hodgepodge which maintains its structure by ShaderLab syntax. To create our segmented blade of grass, we will use a for loop.
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