terravisor/shaders/tessellation_eval.glsl

71 lines
1.9 KiB
GLSL

#version 450 core
layout(quads, fractional_even_spacing, cw) in;
layout(binding = 0) uniform sampler2D heightTexture;
layout(std140, binding = 4) uniform GeoUniforms
{
mat4 PV;
mat4 M;
float minTessellation;
float maxTessellation;
float displacementScale;
int gridDensity;
};
in TC_OUT {
vec3 position;
vec2 texCoord;
} te_in[];
out TE_OUT {
vec3 position;
vec2 texCoord;
vec3 normal;
} te_out;
float getHeight(vec2 uv) {
return texture(heightTexture, uv).r * displacementScale;
}
vec3 calculateSmoothNormal(vec3 pos, vec2 coord) {
// Currently hardcoded to match patch density
float step = 1.0f / (float(gridDensity) * maxTessellation + 1.0f);
// Find surrounding heights
float hLeft = getHeight(coord + vec2(-step, 0.0f));
float hRight = getHeight(coord + vec2(step, 0.0f));
float hUp = getHeight(coord + vec2(0.0f, step));
float hDown = getHeight(coord + vec2(0.0f, -step));
// Calculate tangents
vec3 tangentX = normalize(vec3(step, hRight - hLeft, 0.0));
vec3 tangentY = normalize(vec3(0.0, hUp - hDown, step));
return normalize(cross(tangentY, tangentX));
}
void main() {
// Interpolate texture coordinates
vec2 texCoord = mix(
mix(te_in[0].texCoord, te_in[1].texCoord, gl_TessCoord[0]),
mix(te_in[3].texCoord, te_in[2].texCoord, gl_TessCoord[0]),
gl_TessCoord[1]
);
// Interpolate the original position
vec3 position = mix(
mix(te_in[0].position, te_in[1].position, gl_TessCoord[0]),
mix(te_in[3].position, te_in[2].position, gl_TessCoord[0]),
gl_TessCoord[1]
);
position.z += texture(heightTexture, texCoord).r * displacementScale;
te_out.position = (M*vec4(position, 1.0f)).xyz; // Position in world-space
te_out.texCoord = texCoord;
te_out.normal = calculateSmoothNormal(position, texCoord);
gl_Position = PV*M*vec4(position, 1.0f); // Position in screen-space
}