Graphics Reference
In-Depth Information
Example 14-3
Environment Mapping Vertex Shader
#version 300 es
uniform mat4 u_matViewInverse;
uniform mat4 u_matViewProjection;
uniform vec3 u_lightPosition;
in vec4 a_vertex;
in vec2 a_texcoord0;
in vec3 a_normal;
in vec3 a_binormal;
in vec3 a_tangent;
out vec2 v_texcoord;
out vec3 v_lightDirection;
out vec3 v_normal;
out vec3 v_binormal;
out vec3 v_tangent;
void main( void )
{
// Transform light position into world space
vec3 lightPositionWorld =
(u_matViewInverse * vec4(u_lightPosition, 1.0)).xyz;
// Compute world−space light direction vector
vec3 lightDirectionWorld = lightPositionWorld − a_vertex.xyz;
// Pass the world−space light vector to the fragment shader
v_lightDirection = lightDirectionWorld;
// Transform output position
gl_Position = u_matViewProjection * a_vertex;
// Pass through other attributes
v_texcoord = a_texcoord0.xy;
v_normal = a_normal;
v_binormal = a_binormal;
v_tangent = a_tangent;
}
The vertex shader in this example is very similar to the previous per-
fragment lighting example. The primary difference is that rather than
transforming the light direction vector into tangent space, we keep the
light vector in world space. The reason we must do this is because we
ultimately want to fetch from the cubemap using a world-space reflection
vector. As such, rather than transforming the light vectors into tangent
space, we will transform the normal vector from tangent space into world
