How do I mix a normal map into a reflection of a skybox?

Question

Im triying to create a water example and I know that the first thig requiered is to be able to make a reflection, that is done.

I'm stuck in the next step which is to combine the reflection with a normal map.

What I tried was to load the cube texture as I normally would, calculate the reflection and then load the normal map and combine them in the final step, but the water disappears.

Here's my code:

Vertex Shader

attribute vec3 a_normBT;
attribute vec3 a_normL;
attribute vec3  a_normTan;
attribute vec3 a_posL;
attribute vec2 a_uv;
uniform mat4 u_W;
uniform mat4 u_WVP;
varying vec3 v_normW;
varying vec3 v_normBT;
varying vec3 v_normTan;
varying vec3 v_posW;
varying vec2 v_uv;
void main()
{
    gl_Position  = u_WVP * vec4(a_posL, 1.0);
    v_uv = a_uv;
    v_normW = normalize((u_W*vec4(a_normL, 0.0)).xyz);
    v_normBT = normalize((u_W*vec4(a_normBT,0.0)).xyz);
    v_normTan = normalize((u_W*vec4(a_normTan,0.0)).xyz);
    v_posW = (u_W*vec4(a_posL, 1.0)).xyz;
}

Fragment shader

precision mediump float;
uniform samplerCube u_s_texture;
uniform sampler2D u_s_normalMap;
uniform vec3 u_cpos;// the camera position is already in world space
varying vec3 v_normW;
varying vec3 v_normBT;
varying vec3 v_normTan;
varying vec3 v_posW;
varying vec2 v_uv;
void main()
{
    vec4 tempText =  texture2D(u_s_normalMap, v_uv);
    vec3 Normal = normalize(v_normW);
    vec3 totalDifusse = vec3(0.0,0.0,0.0);
    vec3 totalSpecular = vec3(0.0,0.0,0.0);
    vec3 toEye = u_cpos- v_posW;
    vec3 reflectDir = reflect(normalize(-toEye), normalize(v_normW));  // reflect() in non linear
    gl_FragColor = tempText*textureCube(u_s_texture,reflectDir);
}

What I expect to happen is that the quad I have should have static ripples. Thank you.

What do you see if you do `gl_FragColor= tempText`? Maybe temText.a is equal to 0. Anyway what you probably want to do is take `tempText`, use it's value to change `v_normW` and then reflect it. — Adrian Krupa, Oct 02 '15 at 22:05

score 0 · Answer 1 · edited May 23 '17 at 12:14

Do not know the coordinate system setup of your system and therefore uniforms exact meaning and too lazy to analyze/debug unknown code to help you.

Instead look at this: Normal mapping gone horribly wrong

which is very similar to your task
The main idea is to compute the fragments normal vector in [GCS] global (world coordinate) system
and use that as 3D cubemap texture coordinate where your environment skybox texture is holding...
This is not physically correct (unless surface is fluorescent) but is easy enough as start point and looks good
when done then compute vector from fragment to camera in [GCS]
then compute its reflection around computed normal
and use that as 3D cubemap texture coordinate

Also have you check glGetShaderInfoLog ?

very often a small syntax error prevent GLSL linkage using fixed function instead shader and if you have not compatible written layouts then you see nothing rendered or black ...
see simple compelte GL+GLSL+VAO/VBO example in C++ how the glGetShaderInfoLog is used.

How do I mix a normal map into a reflection of a skybox?

1 Answers1