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Editorial Team
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Asked: 2026-05-19T09:30:49+00:00

My Parallax mapping gives wrong results. I don’t know what can be wrong. The

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My Parallax mapping gives wrong results. I don’t know what can be wrong.

alt text

alt text

The “shadow” is in the wrong place.

Light is pointing from the viewer and goes towards the cube.
Shader program (based on 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 ;
     }

log from cube content (tangents included, the fourth component is handedness):

------------------------------------------------------------------------------------------------------------------
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 

}

What could cause this problem?

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1 Answer

  1. Editorial Team

    As in your previous question, I think you still have the same issue. You forget a minus somewhere, or perhaps performed a cross product in the wrong order.

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