Float4 UnityObjectToClipPos(float3 pos) 同次座標において、オブジェクト空間からカメラのクリップ空間へ点を変換します。これは、mul(UNITYMATRIXMVP, float4(pos, 1.0)) と同等に使用されます。 float3 UnityObjectToViewPos(float3 pos) 点をオブジェクト空間からビュー空間へ変換し. In Raw mode, the center of the screen is 0.5 shift.xy += 0.5f; return shift; In this screenPosition value, the 4th component of the vector, ' w ' (or 'Alpha / a' when you think of the vector as an RGBA colour), is the easiest to understand: it's the world-space depth of the pixel being drawn, measured from the camera, along its viewing axis.
Shaders are used to create many effects, like “water”, “fire” and more.
In order to understand them and become a wizard/witch, we have to learn a bit about meshes first.
- The model-view-projection matrix is used to convert mesh vertices to this space. It is known as clip space, because everything that ends up outside of this cube gets clipped, because it isn't visible. This information actually has nothing to do with shadows directly, but Unity will use it in a later pass. Rendering to Shadow Maps.
- In the previous article, we have seen texture mapping in Unity Cg/HLSL shaders.We will continue our journey with shader passes. In this article, we will see what a shader pass is and learn how we use shader passes in our shaders.
A mesh is made (usually!) by triangles, which means that each triangle has 3 vertices.
You can see the mesh as the structure of your object, built by combining its triangles together.
For example, it can represent a quad (which has two triangles), a cube, a sphere, a character etc.
Now, focusing on vertices, it’s important to know that each single vertex contains some data, more than its position.
In this tutorial, it’s necessary noting UVs.
UVs
UVs are also called texture coordinates and they let you map textures on your objects.
You’re basically saying to the computer: “hey, I want this texture drawn from here to here”. Think at vertices as your “waypoints”.
If you change the UVs (or texture coordinates) of one vertex, you’re also changing the way the texture is displayed on your mesh.
Now that we’ve scratched the topic of meshes, we can finally talk about shader.
Shaders are programs that describe the traits of vertices and pixels.
In other words, via shaders, you can set and change the way the computer renders the meshes.
They’re essential for your games, since you wouldn’t be able to see anything without them.
You can also create cool effects like distortions, portals, grass, water and anything a wizard can do, so: let’s see how they behave.
Their routine is usually this:
The mesh info (vertices, UVs etc.) is read from the computer and is passed to the Vertex Shader.
The Vertex Shader runs once per each vertex and sets your object’s position on Screen. It also prepares the data (like the UVs) that will be used next by the Pixel Shader.
The Pixel Shader runs once per each pixel and renders your object. Here you can apply textures (that’s why you need UVs), change colors, discard pixels etc.
The routine is now complete and it will be executed again in the next frame.
After this theory, it’s time for me to show you a practical example.
Here we have a really basic shader, let’s focus on this part for now, between the CGPROGRAM and ENDCG keywords.
The code you’re watching right now is exactly the routine we’ve discussed before.
With “#pragma vertex vert” we’re saying “Hey computer, I want the “vertex shader” to be executed on this method here, called vert”. (Be aware that in order for them to be paired, they must have the same name).We do the same with our “Pixel Shader”.
Disclaimer: there are two types of “Pixel Shaders”, one called “Fragment” and the other one called “Surface”. In this tutorial we’ll use a Fragment one, but don’t worry: I’ll talk about Surface Shaders and their differences in the next videos/articles.
As you can see from “ #pragma fragment frag” the formatting for the Pixel Shader is the same. “Hey computer, I want the “Fragment shader” to be executed on this method, called frag”.
By writing that, we have defined our vertex and pixel shaders and it’s time to begin our routine.
Placing Vertices
We first need the mesh info, this is why we have the parameter in the vertex method/shader.
Its type is a struct called “appdata” and we can declare which data we need from the mesh.
In this case, we’re telling Unity that we need the position of each vertex.
You can find the semantics for other data in the Unity documentation, linked at the end of this article.
Now that we have this info in the vertex shader, we can place each vertex on the screen, thanks to the function UnityObjectToClipPos(v.vertex) .
We are also preparing the info for the next step of our routine. The data is a struct called “FromVertToFrag” and again, we’re telling that this data contains each vertex position.
As we’ve seen in our Routine, the Pixel Shader needs this info and takes it from the vertex shader. That’s why we can see a “return” on it (and the same struct!).
Also, to easier understand, its type is literally called “From Vertex to Fragment”.
Rendering pixels
Summing up, we now have our vertices placed in the world, but we can’t see our object yet.
Here comes the pixel shader, that runs on all the pixels and renders the mesh.
In it, we’re returning each pixel’s color.
Be aware that a color is composed by four values, Red Green Blue and Alpha (RBGA).
This is why the mesh is red, we’re returning 1, 0 and 0. (and of course transparency is set to one)
If we want a white color, we can write all ones (since white contains all the color).
As an exercise, try turning the mesh blue, then black, and then try creating the colour yellow.
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Now, believe it or not, you’ve just passed the highest obstacle.
If you get how this routine works, you’re already on a good point.
It’s finally time to introduce Properties.
Be aware that I’ll talk about the other things that I’ve left behind (like Passes, Sub Shaders, Tags etc.) in the next video/article, but for now to easier understand shaders in general, take them as they are. Also, the transparency of our objects in this video will always be One. We’ll understand why and we’ll play with it in the next episode.
Properties are variables that show up in the inspector and you can use them in your shaders.
Float
Unityobjecttoclippos Urp
For example, let’s add a variable (a number in this case) that will decide the amount of red in our color.
Start writing our variable inside the Properties block.
Begin with our variable name, then write the label shown in the inspector, its type, and at the end, decide its default value.
The semantics that you have to follow are available in the Unity Documentation, you can find its link at the end of this article.
Let’s check if everything works. Create a material, apply your shader on it and set it on the model. If done correctly, your model is not pink and you can see the “Intensity” popping up in the inspector.
Now, If you want to use this property, you have to write again its type and name inside the Pass (line 27).
Be aware that each variable declaration must be written BEFORE you actually use it. Also, the previously called “FromVertToFrag” is now abbreviated to “v2f”, which still means “vertex to fragment”.
We wanted to set the amount of red so, let’s complete the final step (line 38). As you can see, its amount changes based on the inspector.
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