Unity中的CG编程：实时3D图形入门

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"CG编程在Unity中的应用" "CG编程在Unity"主要涉及的是在Unity引擎中使用CG语言（如Cg或HLSL）来创建实时3D图形的技术。CG语言是NVIDIA公司开发的一种高级着色语言，常用于游戏开发、电影特效等领域，它允许开发者自定义材质和着色器，实现复杂的光照、纹理和透明效果。 1. 基础 - 最小着色器：这是CG编程的基础，通常包括顶点着色器和片段着色器，用于处理几何体的形状和颜色。 - RGB立方体：一种展示颜色空间和变换的方法，帮助理解颜色处理在3D环境中的应用。 - 着色器调试：调试工具和技巧对于找出和修复代码中的错误至关重要。 - 世界空间着色：不在本地坐标系中进行计算，而是直接在世界坐标系下进行，适用于全局光照等复杂情况。 2. 透明表面 - 切口：通过改变透明度来模拟物体内部结构。 - 透明度：控制物体的可见性和穿透性，实现半透明效果。 - 无序透明度：解决因渲染顺序导致的透明物体重叠问题，确保正确显示。 - 轮廓增强：在透明物体边缘增加对比，提高视觉效果。 3. 基本光照 - 漫反射反射：模拟物体表面吸收和散射光线的效果。 - 镜面高光：模拟光线在光滑表面上的强烈反射。 - 双面表面：使物体的两面都能正确接收光照。 - 平滑镜面高光：处理高光区域的平滑过渡。 - 双面平滑表面：结合双面和平滑高光，实现更真实的效果。 - 多光源：处理多个光源对物体的影响，实现复杂的照明环境。 4. 基本纹理 - 纹理化的球体：将纹理映射到3D几何体上，增加视觉细节。 - 光照纹理表面：考虑光照与纹理的交互，创建更真实的表面效果。 - 光泽纹理：模拟物体表面的光泽和反射。 - 透明纹理：结合透明度和纹理，实现如玻璃或水的效果。 - 纹理层：叠加多层纹理，创建更丰富的视觉效果。 5. 3D纹理 - 凹凸贴图光照：利用纹理模拟表面的粗糙度和深度。 - 投影凹凸贴图：将纹理信息投射到3D表面上，增强立体感。 - Cookie纹理：用于控制光源形状，如制作阴影或特殊光效。 - 光衰减：模拟光线随距离减弱的现象，增强光照的真实感。 - 投影器：使用纹理作为光源，可以投射复杂的形状和图案。 6. 环境映射 - 反射表面：创建能够反映周围环境的物体。 - 曲面玻璃：处理曲面的反射效果，如弯曲的镜子或水面。 - 天空盒：模拟无限远的天空背景，提供环境光照。 - 多光源环境映射：结合多光源和环境映射，增强场景的真实感和深度。 "CG编程在Unity"涵盖的内容广泛，从基本的着色器编写到高级的光照和纹理技术，都是为了提升3D场景的视觉质量和性能。学习这些知识可以帮助开发者创建出更为逼真和动态的虚拟世界。

1.3•• Debugging of Shaders

float4 texcoord : TEXCOORD0; // 0th set of texture

// coordinates (a.k.a. “UV”; between 0 and 1)

float4 texcoord1 : TEXCOORD1; // 1st set of texture

// coordinates (a.k.a. “UV”; between 0 and 1)

fixed4 color : COLOR; // color (usually constant)

};

This structure could be used this way:

Shader "Cg shader with all built-in vertex input parameters" {

SubShader {

Pass {

CGPROGRAM

#pragma vertex vert

#pragma fragment frag

struct vertexInput {

float4 vertex : POSITION;

float4 tangent : TANGENT;

float3 normal : NORMAL;

float4 texcoord : TEXCOORD0;

float4 texcoord1 : TEXCOORD1;

fixed4 color : COLOR;

};

struct vertexOutput {

float4 pos : SV_POSITION;

float4 col : TEXCOORD0;

};

vertexOutput vert(vertexInput input)

{

vertexOutput output;

output.pos = mul(UNITY_MATRIX_MVP, input.vertex);

output.col = input.texcoord; // set the output color

// other possibilities to play with:

// output.col = input.vertex;

// output.col = input.tangent;

// output.col = float4(input.normal, 1.0);

// output.col = input.texcoord;

// output.col = input.texcoord1;

// output.col = input.color;

return output;

}

1.3•• Debugging of Shaders

If you focus on the red component or visualize only the red component you should see that it increases from 0 to 1 as

you go around the sphere and after 360‚ drops to 0 again. It actually behaves similar to a longitude coordinate on the

surface of a planet. (In terms of spherical coordinates, it corresponds to the azimuth.)

If the x component of texcoord corresponds to the longitude, one would expect that the y component would

correspond to the latitude (or the inclination in spherical coordinates). However, note that texture coordinates are

always between 0 and 1; therefore, the value is 0 at the bottom (south pole) and 1 at the top (north pole). You can

visualize the y component as green on its own with:

output.col = float4(0.0, input.texcoord.y, 0.0, 1.0);

Texture coordinates are particularly nice to visualize because they are between 0 and 1 just like color components

are. Almost as nice are coordinates of normalized vectors (i.e., vectors of length 1; for example, the normal input

parameter is usually normalized) because they are always between -1 and +1. To map this range to the range from 0

to 1, you add 1 to each component and divide all components by 2, e.g.:

output.col = float4(

(input.normal + float3(1.0, 1.0, 1.0)) / 2.0, 1.0);

Note that normal is a three-dimensional vector. Black corresponds then to the coordinate -1 and full intensity of

one component to the coordinate +1.

If the value that you want to visualize is in another range than 0 to 1 or -1 to +1, you have to map it to the range from

0 to 1, which is the range of color components. If you don't know which values to expect, you just have to

experiment. What helps here is that if you specify color components outside of the range 0 to 1, they are

automatically clamped to this range. I.e., values less than 0 are set to 0 and values greater than 1 are set to 1. Thus,

when the color component is 0 or 1 you know at least that the value is less or greater than what you assumed and

then you can adapt the mapping iteratively until the color component is between 0 and 1.

Debugging Practice

In order to practice the debugging of shaders, this section includes some lines that produce black colors when the

assignment to col in the vertex shader is replaced by each of them. Your task is to figure out for each line, why the

result is black. To this end, you should try to visualize any value that you are not absolutely sure about and map the

values less than 0 or greater than 1 to other ranges such that the values are visible and you have at least an idea in

which range they are. Note that most of the functions and operators are documented in Section “Vector and Matrix

Operations”.

output.col = input.texcoord - float4(1.5, 2.3, 1.1, 0.0);

output.col = float4(input.texcoord.z);

output.col = input.texcoord / tan(0.0);

The following lines require some knowledge about the dot and cross product:

output.col = dot(input.normal, float3(input.tangent)) *

input.texcoord;

output.col = dot(cross(input.normal, float3(input.tangent)),

input.normal) * input.texcoord;

output.col = float4(cross(input.normal, input.normal), 1.0);

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