I'm developing a simple educational project to study OpenGL ES. I'm try to render some simple OBJ models using Blinn-Phong. The first version of the of my implementation calculate all the lighting equation in this way:
#version 300 es
struct material {
vec4 ka;
vec4 kd;
vec4 ks;
float sh;
};
struct pointLight {
vec3 position;
vec4 color;
};
uniform mat4 mvMatrix;
uniform mat4 mvpMatrix;
uniform mat4 normalMatrix;
uniform pointLight light;
uniform material surfaceMaterial;
layout(location = 0) in vec3 inputPosition;
layout(location = 1) in vec3 inputNormal;
out vec4 v_color;
void main() {
//Convert vertex and normal to camera space.
vec3 normal = vec3(normalize(normalMatrix * vec4(inputNormal, 0.0)));
vec4 vertexPositionHomogeneous = mvMatrix * vec4(inputPosition, 1.0);
vec3 vertexPosition = vec3(vertexPositionHomogeneous) / vertexPositionHomogeneous.w;
//Calculate light direction and view direction.
vec3 lightDirection = normalize(light.position - vertexPosition);
vec3 viewPosition = vec3(0.0, 0.0, 1.0);
vec3 viewDirection = normalize(-1.0 * vertexPosition);
//Cosine theta diffuse lambertian component.
float cosTheta = max(0.0, dot(normal, normalize(lightDirection)));
//H vector for specular component.
vec3 h = normalize(lightDirection + viewDirection);
vec4 ambient = surfaceMaterial.ka * light.color;
vec4 diffuse = surfaceMaterial.kd * light.color * cosTheta;
vec4 specular = surfaceMaterial.ks * light.color * pow(max(0.0, dot(h, normal)), surfaceMaterial.sh);
//Output position and color for fragment shader.
v_color = specular;
gl_Position = mvpMatrix * vec4(inputPosition, 1.0);
}
This version doesn't work. This is what I obtain:
If I move the calculation to the fragment shader it works. The is the result:
This image is obtained using a fragment shader that contains the same lighting calculation that I used in the vertex shader above. So my question is: why the vertex shader only version is not working? Am I missing something about how vertex and fragment shaders works?
