ParallaxMap

实际案例：bullet holes

 

基本原理就是偏移当前像素UV，形成高度差。

基本公式：UV + ViewDir.xy *( depth * scale + bias) / viewDir.z；

（ViewDir是贴图空间， depth为深度图中储存值，scale看实际的最大深度，比如（贴图覆盖2*2M的范围，并且最大高度差为0.02M，则scale为0.02/2 = 0.01）， bias不固定，得看实际情况，一般情况下，-0.01会看起来下陷一些，而+0.01就抬高一些。）

reliefMap是指NormalMap中w值为depth。

steepMap技术是指更细微的搜索实际深度。（其中currPoint即为上公式所求值，currHeight为1.0， tStep为currPoint / 25, hStep = 1 / 25, iStep = 25）

float TraceLinear(sampler2D m_HeightMap, inout vec2 CurrPoint, inout float CurrHeight, vec2 tStep, float hStep, float mipLevel, float iSteps, inout float Intersected) {
    float tHeight = 0.0;
    for(float i = 0.0; i < iSteps; i+= 1.0)   {
        // The trace will stop at the point before the actuall intersection with m_HeightMap field happens
        tHeight = 1.0f - texture2DLod( m_HeightMap, CurrPoint - tStep, mipLevel ).x;

        if( (CurrHeight - hStep > tHeight) && (CurrHeight > 0) ) {
            CurrHeight -= hStep;
            CurrPoint  -= tStep;
        }
        else {
            Intersected = 1.0f;
            i = iSteps;
        }
    }
    return tHeight;
}

 

JME3 lighting.frag例子

    

float h;
         h = texture2D(m_ParallaxMap, texCoord).r;
          h = texture2D(m_NormalMap, texCoord).a;
       float heightScale = 0.05;
       float heightBias = heightScale * -0.5;
       vec3 normView = normalize(vViewDir);      // vViewDir为贴图空间

       h = (h * heightScale + heightBias) * normView.z;

       newTexCoord = texCoord + (h * -normView.xy);