Hello all!
I closely followed the following tutorial for basic OpenGL tesselation:
http://ogldev.atspace.co.uk/www/tutorial30/tutorial30.html
I am using it in a slightly different context with Deferred Rendering.
All I did was added a simple tesselation control shader to completely unalter the triangle patches:
Tesselation Control Shadee:
#version 420
// define the number of CPs in the output patch
layout (vertices = 3) out;
uniform vec3 gEyeWorldPos;
// attributes of the input CPs
in vec3 WorldPos_CS_in[];
in vec2 TexCoord_CS_in[];
in vec3 Normal_CS_in [];
in vec3 Tangent_CS_in [];
// attributes of the output CPs
out vec3 WorldPos_ES_in[];
out vec2 TexCoord_ES_in[];
out vec3 Normal_ES_in[];
out vec3 Tangent_ES_in[];
float GetTessLevel(float Distance0, float Distance1)
{
float AvgDistance = (Distance0 + Distance1) / 2.0;
if (AvgDistance <= 2.0) {
return 10.0;
}
else if (AvgDistance <= 5.0) {
return 7.0;
}
else {
return 3.0;
}
}
void main()
{
// Set the control points of the output patch
TexCoord_ES_in[gl_InvocationID] = TexCoord_CS_in[gl_InvocationID];
Normal_ES_in[gl_InvocationID] = Normal_CS_in[gl_InvocationID];
Tangent_ES_in[gl_InvocationID] = Tangent_CS_in[gl_InvocationID];
WorldPos_ES_in[gl_InvocationID] = WorldPos_CS_in[gl_InvocationID];
// Calculate the distance from the camera to the three control points
float EyeToVertexDistance0 = distance(gEyeWorldPos, WorldPos_ES_in[0]);
float EyeToVertexDistance1 = distance(gEyeWorldPos, WorldPos_ES_in[1]);
float EyeToVertexDistance2 = distance(gEyeWorldPos, WorldPos_ES_in[2]);
// Calculate the tessellation levels
gl_TessLevelOuter[0] = GetTessLevel(EyeToVertexDistance1, EyeToVertexDistance2);
gl_TessLevelOuter[1] = GetTessLevel(EyeToVertexDistance2, EyeToVertexDistance0);
gl_TessLevelOuter[2] = GetTessLevel(EyeToVertexDistance0, EyeToVertexDistance1);
gl_TessLevelInner[0] = gl_TessLevelOuter[2];
}
And a simple Tesselation Evaluation Shader (this will ultimately sample from a Displacement Map, but at the moment I have the displacement commented out)
#version 420
layout(triangles, equal_spacing, ccw) in;
uniform mat4 gVP;
uniform sampler2D gDisplacementMap;
uniform float gDispFactor;
in vec3 WorldPos_ES_in[];
in vec2 TexCoord_ES_in[];
in vec3 Normal_ES_in[];
in vec3 Tangent_ES_in[];
out vec3 WorldPos_FS_in;
out vec2 TexCoord_FS_in;
out vec3 Normal_FS_in;
out vec3 Tangent_FS_in;
vec2 interpolate2D(vec2 v0, vec2 v1, vec2 v2)
{
return vec2(gl_TessCoord.x) * v0 + vec2(gl_TessCoord.y) * v1 + vec2(gl_TessCoord.z) * v2;
}
vec3 interpolate3D(vec3 v0, vec3 v1, vec3 v2)
{
return vec3(gl_TessCoord.x) * v0 + vec3(gl_TessCoord.y) * v1 + vec3(gl_TessCoord.z) * v2;
}
void main()
{
// Interpolate the attributes of the output vertex using the barycentric coordinates
TexCoord_FS_in = interpolate2D(TexCoord_ES_in[0], TexCoord_ES_in[1], TexCoord_ES_in[2]);
Normal_FS_in = interpolate3D(Normal_ES_in[0], Normal_ES_in[1], Normal_ES_in[2]);
Normal_FS_in = normalize(Normal_FS_in);
Tangent_FS_in = interpolate3D(Tangent_ES_in[0], Tangent_ES_in[1], Tangent_ES_in[2]);
Tangent_FS_in = normalize(Tangent_FS_in);
WorldPos_FS_in = interpolate3D(WorldPos_ES_in[0], WorldPos_ES_in[1], WorldPos_ES_in[2]);
// Displace the vertex along the normal
//float Displacement = texture(gDisplacementMap, TexCoord_FS_in.xy).x;
//WorldPos_FS_in += Normal_FS_in * Displacement * gDispFactor;
gl_Position = gVP * vec4(WorldPos_FS_in, 1.0);
}
I am using NVidia NSight. If I do not attach the Control and Evaluation Shaders, the shader executes just fine. I can put breakpoints on my vertex and fragment shader in NSight, and the shaders are executing and I'm seeing what I'd expect on screen.
If I do attach the tesselation shaders, I see nothing on screen and putting breakpoints on the Vertex or Fragment shader doesn't work, indicating that they are not executing at all.
NSight requires that you are running OpenGL 4.x to run the shader debugger, so my OpenGL version should be fine. I remembered to call: glPatchParameteri(GL_PATCH_VERTICES, 3); and I checked my GL_MAX_PATCH_VERTICES and the value is 32.
I read that I may need to use GL_PATCHES as my primitive type, so I am using this in my draw call:
glDrawElementsBaseVertex(GL_PATCHES, numIndices,
GL_UNSIGNED_INT,
(void*)(sizeof(unsigned int) * mesh->m_index_offset),
start); still the Shader refuses to execute.
Kind of at my wits end here. :\ does anyone have any ideas?
Thanks!
