PlayCanvas PBR材质shader代码分析(vertex shader)

顶点shader主要对顶点坐标变换，将顶点坐标从local->world->view->clip 空间变换

local空间:模型物体坐标系

world空间:世界空间坐标系

view空间: 相机空间

clip空间: 裁剪空间

local->world空间简化后其实就是这么一行代码:

vec4 posW = dModelMatrix * vec4(localPos, 1.0);

此图由https://tinygltf.xyz/drawgeometry/网站脚本编写后截图输出

dModelMatrix就是将顶点local坐标系转换到了世界坐标系下。

dModelMatrix是通过getModelMatrix()方法获取

mat4 getModelMatrix() {
    #ifdef DYNAMICBATCH
        return getBoneMatrix(vertex_boneIndices);
        #elif defined(SKIN)
        return matrix_model * (getBoneMatrix(vertex_boneIndices.x) * vertex_boneWeights.x +
        getBoneMatrix(vertex_boneIndices.y) * vertex_boneWeights.y+
        getBoneMatrix(vertex_boneIndices.z) * vertex_boneWeights.z +
        getBoneMatrix(vertex_boneIndices.w) * vertex_boneWeights.w);
        #elif defined(INSTANCING)
        return mat4(instance_line1, instance_line2, instance_line3, instance_line4);
    #else
        return matrix_model;
    #endif
}

从代码可以看出这里有不同分支代码，通过不一样的方式得到modelMatrix,如果没有蒙皮动画就是简单的通过外部传进来的全局modelMatrix给返回即可

如果有蒙皮动画会将返回modelMatrix * boneMatrix，意思就是顶点local坐标先会进行一次骨骼变化（通过骨骼矩阵）,然后再通过modelMatrix转到世界空间,

boneMatrix的计算方式会通过顶点权重以及对应的骨骼的骨骼矩阵进行加和。

world->clip空间简化后:

screenPos = matrix_viewProjection * posW;

其实就是将之前得到的顶点世界坐标通过matrix_viewprojection矩阵变换到裁剪空间，这里虽然写的是screenPos其实这里坐标还不是屏幕坐标，它只是未归一化的clip空间，然后到fragment shader时候会除以w然后裁剪后xyz归一到[-1,1]的NDC空间

vertex shader只需要输出clip空间的坐标即可也就是getPosition()返回给gl_Position出去。

gl_Position = getPosition();

void main(void) {
    gl_Position = getPosition();
    vPositionW = getWorldPosition();
    vNormalW = dNormalW = getNormal();
    vec2 uv0 = getUv0();
    vUv0 = uv0;
    vVertexColor = vertex_color;
}

后面几行代码getWorldPosition()，getNormal()，getUv0(),计算输出顶点的世界坐标以及世界空间法线方向和uv坐标给fragment shader用来光照着色使用!

完整代码如下:

#version 300 es


#define attribute in
#define varying out
#define texture2D texture
#define GL2
#define VERTEXSHADER
varying vec4 vVertexColor;
varying vec3 vPositionW;
varying vec3 vNormalW;
varying vec2 vUv0;
attribute vec3 vertex_position;
attribute vec3 vertex_normal;
attribute vec4 vertex_tangent;
attribute vec2 vertex_texCoord0;
attribute vec2 vertex_texCoord1;
attribute vec4 vertex_color;
uniform mat4 matrix_viewProjection;
uniform mat4 matrix_model;
uniform mat3 matrix_normal;
vec3 dPositionW;
mat4 dModelMatrix;
mat3 dNormalMatrix;
vec3 dLightPosW;
vec3 dLightDirNormW;
vec3 dNormalW;
#ifdef NINESLICED
    vec2 getUv0() {
        vec2 uv = vertex_position.xz;
        // offset inner vertices inside
 
        // (original vertices must be in [-1;1] range)
        vec2 positiveUnitOffset = clamp(vertex_position.xz, vec2(0.0), vec2(1.0));
        vec2 negativeUnitOffset = clamp(-vertex_position.xz, vec2(0.0), vec2(1.0));
        uv += (-positiveUnitOffset * innerOffset.xy + negativeUnitOffset * innerOffset.zw) * vertex_texCoord0.xy;
        uv = uv * -0.5 + 0.5;
        uv = uv * atlasRect.zw + atlasRect.xy;
        vMask = vertex_texCoord0.xy;
        return uv;
    }
#else
    vec2 getUv0() {
        return vertex_texCoord0;
    }
#endif
attribute vec4 vertex_boneWeights;
attribute vec4 vertex_boneIndices;
uniform sampler2D texture_poseMap;
uniform vec2 texture_poseMapSize;
mat4 getBoneMatrix(const in float i) {
    float j = i * 4.0;
    float x = mod(j, float(texture_poseMapSize.x));
    float y = floor(j / float(texture_poseMapSize.x));
    float dx = 1.0 / float(texture_poseMapSize.x);
    float dy = 1.0 / float(texture_poseMapSize.y);
    y = dy * (y + 0.5);
    vec4 v1 = texture2D(texture_poseMap, vec2(dx * (x + 0.5), y));
    vec4 v2 = texture2D(texture_poseMap, vec2(dx * (x + 1.5), y));
    vec4 v3 = texture2D(texture_poseMap, vec2(dx * (x + 2.5), y));
    vec4 v4 = texture2D(texture_poseMap, vec2(dx * (x + 3.5), y));
    mat4 bone = mat4(v1, v2, v3, v4);
    return bone;
}
#define SKIN
#ifdef PIXELSNAP
    uniform vec4 uScreenSize;
#endif
mat4 getModelMatrix() {
#ifdefDYNAMICBATCH
        return getBoneMatrix(vertex_boneIndices);
#elifdefined(SKIN)
        return matrix_model * (getBoneMatrix(vertex_boneIndices.x) * vertex_boneWeights.x +
        getBoneMatrix(vertex_boneIndices.y) * vertex_boneWeights.y+
        getBoneMatrix(vertex_boneIndices.z) * vertex_boneWeights.z +
        getBoneMatrix(vertex_boneIndices.w) * vertex_boneWeights.w);
#elifdefined(INSTANCING)
        return mat4(instance_line1, instance_line2, instance_line3, instance_line4);
#else
        return matrix_model;
#endif
}
vec4 getPosition() {
    dModelMatrix = getModelMatrix();
    vec3 localPos = vertex_position;
#ifdefNINESLICED
        // outer and inner vertices are at the same position, scale both
        localPos.xz *= outerScale;
        // offset inner vertices inside
 
        // (original vertices must be in [-1;1] range)
        vec2 positiveUnitOffset = clamp(vertex_position.xz, vec2(0.0), vec2(1.0));
        vec2 negativeUnitOffset = clamp(-vertex_position.xz, vec2(0.0), vec2(1.0));
        localPos.xz += (-positiveUnitOffset * innerOffset.xy + negativeUnitOffset * innerOffset.zw) * vertex_texCoord0.xy;
        vTiledUv = (localPos.xz - outerScale + innerOffset.xy) * -0.5 + 1.0; // uv = local pos - inner corner
 
        localPos.xz *= -0.5; // move from -1;1 to -0.5;0.5
 
        localPos = localPos.xzy;
#endif
    vec4 posW = dModelMatrix * vec4(localPos, 1.0);
#ifdefSCREENSPACE
        posW.zw = vec2(0.0, 1.0);
#endif
    dPositionW = posW.xyz;
    vec4 screenPos;
#ifdefUV1LAYOUT
        screenPos = vec4(vertex_texCoord1.xy * 2.0 - 1.0, 0.5, 1);
#else
#ifdefSCREENSPACE
            screenPos = posW;
#else
            screenPos = matrix_viewProjection * posW;
#endif
#ifdefPIXELSNAP
            // snap vertex to a pixel boundary
            screenPos.xy = (screenPos.xy * 0.5) + 0.5;
            screenPos.xy *= uScreenSize.xy;
            screenPos.xy = floor(screenPos.xy);
            screenPos.xy *= uScreenSize.zw;
            screenPos.xy = (screenPos.xy * 2.0) - 1.0;
#endif
#endif
    return screenPos;
}
vec3 getWorldPosition() {
    return dPositionW;
}
vec3 getNormal() {
#ifdefSKIN
        dNormalMatrix = mat3(dModelMatrix[0].xyz, dModelMatrix[1].xyz, dModelMatrix[2].xyz);
#elifdefined(INSTANCING)
        dNormalMatrix = mat3(instance_line1.xyz, instance_line2.xyz, instance_line3.xyz);
#else
        dNormalMatrix = matrix_normal;
#endif
    return normalize(dNormalMatrix * vertex_normal);
}
void main(void) {
    gl_Position = getPosition();
    vPositionW = getWorldPosition();
    vNormalW = dNormalW = getNormal();
    vec2 uv0 = getUv0();
    vUv0 = uv0;
    vVertexColor = vertex_color;
}

#version 300 es


#define attribute in
#define varying out
#define texture2D texture
#define GL2
#define VERTEXSHADER
varying vec4 vVertexColor;
varying vec3 vPositionW;
varying vec3 vNormalW;
varying vec2 vUv0;
attribute vec3 vertex_position;
attribute vec3 vertex_normal;
attribute vec4 vertex_tangent;
attribute vec2 vertex_texCoord0;
attribute vec2 vertex_texCoord1;
attribute vec4 vertex_color;
uniform mat4 matrix_viewProjection;
uniform mat4 matrix_model;
uniform mat3 matrix_normal;
vec3 dPositionW;
mat4 dModelMatrix;
mat3 dNormalMatrix;
vec3 dLightPosW;
vec3 dLightDirNormW;
vec3 dNormalW;
#ifdef NINESLICED
    vec2 getUv0() {
        vec2 uv = vertex_position.xz;
        // offset inner vertices inside
 
        // (original vertices must be in [-1;1] range)
        vec2 positiveUnitOffset = clamp(vertex_position.xz, vec2(0.0), vec2(1.0));
        vec2 negativeUnitOffset = clamp(-vertex_position.xz, vec2(0.0), vec2(1.0));
        uv += (-positiveUnitOffset * innerOffset.xy + negativeUnitOffset * innerOffset.zw) * vertex_texCoord0.xy;
        uv = uv * -0.5 + 0.5;
        uv = uv * atlasRect.zw + atlasRect.xy;
        vMask = vertex_texCoord0.xy;
        return uv;
    }
#else
    vec2 getUv0() {
        return vertex_texCoord0;
    }
#endif
attribute vec4 vertex_boneWeights;
attribute vec4 vertex_boneIndices;
uniform sampler2D texture_poseMap;
uniform vec2 texture_poseMapSize;
mat4 getBoneMatrix(const in float i) {
    float j = i * 4.0;
    float x = mod(j, float(texture_poseMapSize.x));
    float y = floor(j / float(texture_poseMapSize.x));
    float dx = 1.0 / float(texture_poseMapSize.x);
    float dy = 1.0 / float(texture_poseMapSize.y);
    y = dy * (y + 0.5);
    vec4 v1 = texture2D(texture_poseMap, vec2(dx * (x + 0.5), y));
    vec4 v2 = texture2D(texture_poseMap, vec2(dx * (x + 1.5), y));
    vec4 v3 = texture2D(texture_poseMap, vec2(dx * (x + 2.5), y));
    vec4 v4 = texture2D(texture_poseMap, vec2(dx * (x + 3.5), y));
    mat4 bone = mat4(v1, v2, v3, v4);
    return bone;
}
#define SKIN
#ifdef PIXELSNAP
    uniform vec4 uScreenSize;
#endif
mat4 getModelMatrix() {
#ifdefDYNAMICBATCH
        return getBoneMatrix(vertex_boneIndices);
#elifdefined(SKIN)
        return matrix_model * (getBoneMatrix(vertex_boneIndices.x) * vertex_boneWeights.x +
        getBoneMatrix(vertex_boneIndices.y) * vertex_boneWeights.y+
        getBoneMatrix(vertex_boneIndices.z) * vertex_boneWeights.z +
        getBoneMatrix(vertex_boneIndices.w) * vertex_boneWeights.w);
#elifdefined(INSTANCING)
        return mat4(instance_line1, instance_line2, instance_line3, instance_line4);
#else
        return matrix_model;
#endif
}
vec4 getPosition() {
    dModelMatrix = getModelMatrix();
    vec3 localPos = vertex_position;
#ifdefNINESLICED
        // outer and inner vertices are at the same position, scale both
        localPos.xz *= outerScale;
        // offset inner vertices inside
 
        // (original vertices must be in [-1;1] range)
        vec2 positiveUnitOffset = clamp(vertex_position.xz, vec2(0.0), vec2(1.0));
        vec2 negativeUnitOffset = clamp(-vertex_position.xz, vec2(0.0), vec2(1.0));
        localPos.xz += (-positiveUnitOffset * innerOffset.xy + negativeUnitOffset * innerOffset.zw) * vertex_texCoord0.xy;
        vTiledUv = (localPos.xz - outerScale + innerOffset.xy) * -0.5 + 1.0; // uv = local pos - inner corner
 
        localPos.xz *= -0.5; // move from -1;1 to -0.5;0.5
 
        localPos = localPos.xzy;
#endif
    vec4 posW = dModelMatrix * vec4(localPos, 1.0);
#ifdefSCREENSPACE
        posW.zw = vec2(0.0, 1.0);
#endif
    dPositionW = posW.xyz;
    vec4 screenPos;
#ifdefUV1LAYOUT
        screenPos = vec4(vertex_texCoord1.xy * 2.0 - 1.0, 0.5, 1);
#else
#ifdefSCREENSPACE
            screenPos = posW;
#else
            screenPos = matrix_viewProjection * posW;
#endif
#ifdefPIXELSNAP
            // snap vertex to a pixel boundary
            screenPos.xy = (screenPos.xy * 0.5) + 0.5;
            screenPos.xy *= uScreenSize.xy;
            screenPos.xy = floor(screenPos.xy);
            screenPos.xy *= uScreenSize.zw;
            screenPos.xy = (screenPos.xy * 2.0) - 1.0;
#endif
#endif
    return screenPos;
}
vec3 getWorldPosition() {
    return dPositionW;
}
vec3 getNormal() {
#ifdefSKIN
        dNormalMatrix = mat3(dModelMatrix[0].xyz, dModelMatrix[1].xyz, dModelMatrix[2].xyz);
#elifdefined(INSTANCING)
        dNormalMatrix = mat3(instance_line1.xyz, instance_line2.xyz, instance_line3.xyz);
#else
        dNormalMatrix = matrix_normal;
#endif
    return normalize(dNormalMatrix * vertex_normal);
}
void main(void) {
    gl_Position = getPosition();
    vPositionW = getWorldPosition();
    vNormalW = dNormalW = getNormal();
    vec2 uv0 = getUv0();
    vUv0 = uv0;
    vVertexColor = vertex_color;
}

来源：https://www.cnblogs.com/zzatp/p/11334626.html

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