GLSL中的视差映射问题，OpenGL

Question

我的视差贴图效果不正确，我不知道哪里出了问题。


“阴影”位置不对。
光线从观察者处指向立方体。
着色器程序（基于dhpoware.com）：

[vert]
     varying vec3 lightDir;            
     varying vec3 viewDir;
     attribute vec4 tangent;
     void main() 
     { 
     gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
     gl_TexCoord[0] = gl_MultiTexCoord0;
     vec3 vertexPos = vec3(gl_ModelViewMatrix * gl_Vertex);
     vec3 n = normalize(gl_NormalMatrix * gl_Normal);
     vec3 t = normalize(gl_NormalMatrix * tangent.xyz);
     vec3 b = cross(n, t) * tangent.w;
     mat3 tbnMatrix = mat3(t.x, b.x, n.x,
                           t.y, b.y, n.y,
                           t.z, b.z, n.z);
     lightDir = (gl_LightSource[0].position.xyz - vertexPos) / 1000.0;
     lightDir = tbnMatrix * lightDir;
     viewDir = -vertexPos;
     viewDir = tbnMatrix * viewDir;
     } 

    [frag]
     varying vec3 lightDir;            
     varying vec3 viewDir;
     uniform sampler2D diffuseMap;
     uniform sampler2D normalMap;
     uniform sampler2D heightMap;
     uniform float scale;
     uniform float bias;
     void main() 
     { 
     vec3 v = normalize(viewDir);
     vec2 TexCoord = gl_TexCoord[0].st;
    {
     float height = texture2D(heightMap, gl_TexCoord[0].st).r;
     height = height * scale + bias;
     TexCoord = gl_TexCoord[0].st + (height * v.xy); 
    }
     vec3 l = lightDir;
     float atten = max(0.0, 1.0 - dot(l, l));
     l = normalize(l);
     vec3 n = normalize(texture2D(normalMap, TexCoord).rgb * 2.0 - 1.0);
     vec3 h = normalize(l + v);
     float nDotL = max(0.0, dot(n, l));
     float nDotH = max(0.0, dot(n, h));
     float power = (nDotL == 0.0) ? 0.0 : pow(nDotH, gl_FrontMaterial.shininess);
     vec4 ambient = gl_FrontLightProduct[0].ambient * atten;
     vec4 diffuse = gl_FrontLightProduct[0].diffuse * nDotL * atten;
     vec4 specular = gl_FrontLightProduct[0].specular * power * atten;
     vec4 color = gl_FrontLightModelProduct.sceneColor + ambient + diffuse + specular;color *= texture2D(diffuseMap,TexCoord);
     gl_FragColor = color ;
     } 

来自立方体内容的日志（包含切线，第四个分量是左右手）：

------------------------------------------------------------------------------------------------------------------
VecContainer<Vertex> vertices = 

size: 36
space: 36
{
-4.000000, -4.000000, -4.000000, 
-4.000000, 4.000000, -4.000000, 
4.000000, 4.000000, -4.000000, 
4.000000, 4.000000, -4.000000, 
4.000000, -4.000000, -4.000000, 
-4.000000, -4.000000, -4.000000, 
-4.000000, -4.000000, -4.000000, 
4.000000, -4.000000, -4.000000, 
4.000000, -4.000000, 4.000000, 
4.000000, -4.000000, 4.000000, 
-4.000000, -4.000000, 4.000000, 
-4.000000, -4.000000, -4.000000, 
-4.000000, -4.000000, -4.000000, 
-4.000000, -4.000000, 4.000000, 
-4.000000, 4.000000, 4.000000, 
-4.000000, 4.000000, 4.000000, 
-4.000000, 4.000000, -4.000000, 
-4.000000, -4.000000, -4.000000, 
4.000000, -4.000000, -4.000000, 
4.000000, 4.000000, -4.000000, 
4.000000, 4.000000, 4.000000, 
4.000000, 4.000000, 4.000000, 
4.000000, -4.000000, 4.000000, 
4.000000, -4.000000, -4.000000, 
-4.000000, 4.000000, -4.000000, 
-4.000000, 4.000000, 4.000000, 
4.000000, 4.000000, 4.000000, 
4.000000, 4.000000, 4.000000, 
4.000000, 4.000000, -4.000000, 
-4.000000, 4.000000, -4.000000, 
-4.000000, -4.000000, 4.000000, 
4.000000, -4.000000, 4.000000, 
4.000000, 4.000000, 4.000000, 
4.000000, 4.000000, 4.000000, 
-4.000000, 4.000000, 4.000000, 
-4.000000, -4.000000, 4.000000, 

}

------------------------------------------------------------------------------------------------------------------
VecContainer<Vertex> texcoords = 

size: 36
space: 36
{
0.000000, 0.000000, 
0.000000, 1.000000, 
1.000000, 1.000000, 
1.000000, 1.000000, 
1.000000, 0.000000, 
0.000000, 0.000000, 
0.000000, 0.000000, 
1.000000, 0.000000, 
1.000000, 1.000000, 
1.000000, 1.000000, 
0.000000, 1.000000, 
0.000000, 0.000000, 
0.000000, 0.000000, 
1.000000, 0.000000, 
1.000000, 1.000000, 
1.000000, 1.000000, 
0.000000, 1.000000, 
0.000000, 0.000000, 
1.000000, 0.000000, 
1.000000, 1.000000, 
0.000000, 1.000000, 
0.000000, 1.000000, 
0.000000, 0.000000, 
1.000000, 0.000000, 
0.000000, 1.000000, 
0.000000, 0.000000, 
1.000000, 0.000000, 
1.000000, 0.000000, 
1.000000, 1.000000, 
0.000000, 1.000000, 
0.000000, 0.000000, 
1.000000, 0.000000, 
1.000000, 1.000000, 
1.000000, 1.000000, 
0.000000, 1.000000, 
0.000000, 0.000000, 

}

------------------------------------------------------------------------------------------------------------------
VecContainer<Vertex> normals = 

size: 36
space: 36
{
0.000000, 0.000000, -1.000000, 
0.000000, 0.000000, -1.000000, 
0.000000, 0.000000, -1.000000, 
0.000000, 0.000000, -1.000000, 
0.000000, 0.000000, -1.000000, 
0.000000, 0.000000, -1.000000, 
0.000000, -1.000000, 0.000000, 
0.000000, -1.000000, 0.000000, 
0.000000, -1.000000, 0.000000, 
0.000000, -1.000000, 0.000000, 
0.000000, -1.000000, 0.000000, 
0.000000, -1.000000, 0.000000, 
-1.000000, 0.000000, 0.000000, 
-1.000000, 0.000000, 0.000000, 
-1.000000, 0.000000, 0.000000, 
-1.000000, 0.000000, 0.000000, 
-1.000000, 0.000000, 0.000000, 
-1.000000, 0.000000, 0.000000, 
1.000000, 0.000000, 0.000000, 
1.000000, 0.000000, 0.000000, 
1.000000, 0.000000, 0.000000, 
1.000000, 0.000000, 0.000000, 
1.000000, 0.000000, 0.000000, 
1.000000, 0.000000, 0.000000, 
0.000000, 1.000000, 0.000000, 
0.000000, 1.000000, 0.000000, 
0.000000, 1.000000, 0.000000, 
0.000000, 1.000000, 0.000000, 
0.000000, 1.000000, 0.000000, 
0.000000, 1.000000, 0.000000, 
0.000000, 0.000000, 1.000000, 
0.000000, 0.000000, 1.000000, 
0.000000, 0.000000, 1.000000, 
0.000000, 0.000000, 1.000000, 
0.000000, 0.000000, 1.000000, 
0.000000, 0.000000, 1.000000, 

}

------------------------------------------------------------------------------------------------------------------
VecContainer<tangent>* tangents = 

size: 36
space: 36
{
1.000000, -0.000000, 0.000000, 1.000000, 
1.000000, -0.000000, 0.000000, 1.000000, 
1.000000, -0.000000, 0.000000, 1.000000, 
1.000000, -0.000000, 0.000000, 1.000000, 
1.000000, -0.000000, 0.000000, 1.000000, 
1.000000, -0.000000, 0.000000, 1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
0.000000, 0.000000, 1.000000, -1.000000, 
0.000000, 0.000000, 1.000000, -1.000000, 
0.000000, 0.000000, 1.000000, -1.000000, 
0.000000, 0.000000, 1.000000, -1.000000, 
0.000000, 0.000000, 1.000000, -1.000000, 
0.000000, 0.000000, 1.000000, -1.000000, 
0.000000, 0.000000, -1.000000, -1.000000, 
0.000000, 0.000000, -1.000000, -1.000000, 
0.000000, 0.000000, -1.000000, -1.000000, 
0.000000, 0.000000, -1.000000, -1.000000, 
0.000000, 0.000000, -1.000000, -1.000000, 
0.000000, 0.000000, -1.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, 0.000000, -1.000000, 
1.000000, 0.000000, -0.000000, -1.000000, 
1.000000, 0.000000, -0.000000, -1.000000, 
1.000000, 0.000000, -0.000000, -1.000000 

}

------------------------------------------------------------------------------------------------------------------
VecContainer<GLuint> indices = 

size: 12
space: 12
{
3, 4, 5, 
6, 7, 8, 
9, 10, 11, 
12, 13, 14, 
15, 16, 17, 
18, 19, 20, 
21, 22, 23, 
24, 25, 26, 
27, 28, 29, 
30, 31, 32, 
33, 34, 35, 
0, 1, 2 

}

什么可能导致这个问题？

- Pythagoras of Samos

---

重复：https://dev59.com/9VPTa4cB1Zd3GeqPkZKi - GManNickG

我不同意第二张图片的“好结果”。阴影仍然朝向相机，而您说光源在相机处。 - Ben Voigt

感谢您的评论，Ben。您说得对，虽然这个问题已经过时并且已经解决了，但我只是进行了一些编辑以更好地匹配SO格式，忘记了它会在第一页上显示。 - Pythagoras of Samos

Answer 1

就像你之前提出的问题一样，我认为你仍然存在同样的问题。你可能忘记了减号的位置，或者是以错误的顺序进行了叉积运算。

- Yakov Galka

---

同意。如果阴影在某些面或某些角度上是正确的，但在其他情况下是错误的，则说明您的某些切线方向是错误的。 - Asher Dunn