Understanding tessellation shaders
I am trying to use the tessellation shaders in OpenGL ES 3.2, and have tried to follow 2 different tutorials without success.
I am currently drawing a flat rectangle, the goal is to elevate its surface. I receive the vertices in the vertex shader:
#version 320 es
layout (location = 0) in vec3 position;
out vec3 v_position;
uniform mat4 model_matrix;
uniform mat4 mvp_matrix;
void main() {
vec4 pos = vec4(position, 1.0);
v_position = vec3(model_matrix * pos);
gl_Position = mvp_matrix * vec4(position, 1.0);
}
Attempt to tessellate in the tessellation control shader:
#version 320 es
layout (vertices = 3) out;
in vec3 v_position;
out vec3 t_position;
void main()
{
// Set the control points of the output patch
t_position[gl_InvocationID] = v_position[gl_InvocationID];
// Calculate the tessellation levels
gl_TessLevelOuter[0] = 3.0;
gl_TessLevelOuter[1] = 3.0;
gl_TessLevelOuter[2] = 3.0;
gl_TessLevelInner[0] = gl_TessLevelOuter[2];
}
And then try to make a minimum working evaluation shader:
#version 320 es
layout(triangles, equal_spacing, ccw) in;
in vec3 t_position;
out vec3 f_position;
uniform mat4 mvp_matrix;
void main() {
f_position = t_position[0];
gl_Position = mvp_matrix * vec4(f_position, 1.0);
}
I call these shaders using glDrawArrays(GL_PATCHES, 0, vertex_num). However currently I see no output when attempting to tessellate. if instead I remove the tessellation shaders and draw with only the vertex and fragment shaders (after tweaking so that they compile). I do see the rectangle mesh, so I am confident the issue is in my shaders.
I am not getting compilation errors, and calling glGetError() reports no error, so it's my logic that I think is wrong.
Edit:
Immediately prior to the draw call I also do:
glPatchParameteri(GL_PATCH_VERTICES, 3);
opengl-es glsl shader tessellation
edited Nov 14 '18 at 19:51
genpfault
42.2k95399
asked Nov 14 '18 at 19:17
MakoganMakogan
1,7841829
|
show 2 more comments
I am trying to use the tessellation shaders in OpenGL ES 3.2, and have tried to follow 2 different tutorials without success.
I am currently drawing a flat rectangle, the goal is to elevate its surface. I receive the vertices in the vertex shader:
#version 320 es
layout (location = 0) in vec3 position;
out vec3 v_position;
uniform mat4 model_matrix;
uniform mat4 mvp_matrix;
void main() {
vec4 pos = vec4(position, 1.0);
v_position = vec3(model_matrix * pos);
gl_Position = mvp_matrix * vec4(position, 1.0);
}
Attempt to tessellate in the tessellation control shader:
#version 320 es
layout (vertices = 3) out;
in vec3 v_position;
out vec3 t_position;
void main()
{
// Set the control points of the output patch
t_position[gl_InvocationID] = v_position[gl_InvocationID];
// Calculate the tessellation levels
gl_TessLevelOuter[0] = 3.0;
gl_TessLevelOuter[1] = 3.0;
gl_TessLevelOuter[2] = 3.0;
gl_TessLevelInner[0] = gl_TessLevelOuter[2];
}
And then try to make a minimum working evaluation shader:
#version 320 es
layout(triangles, equal_spacing, ccw) in;
in vec3 t_position;
out vec3 f_position;
uniform mat4 mvp_matrix;
void main() {
f_position = t_position[0];
gl_Position = mvp_matrix * vec4(f_position, 1.0);
}
I call these shaders using glDrawArrays(GL_PATCHES, 0, vertex_num). However currently I see no output when attempting to tessellate. if instead I remove the tessellation shaders and draw with only the vertex and fragment shaders (after tweaking so that they compile). I do see the rectangle mesh, so I am confident the issue is in my shaders.
I am not getting compilation errors, and calling glGetError() reports no error, so it's my logic that I think is wrong.
Edit:
Immediately prior to the draw call I also do:
glPatchParameteri(GL_PATCH_VERTICES, 3);
opengl-es glsl shader tessellation
edited Nov 14 '18 at 19:51
genpfault
42.2k95399
asked Nov 14 '18 at 19:17
MakoganMakogan
1,7841829
You have to setglPatchParameteri( GL_PATCH_VERTICES, 3 )before the draw call.
– Rabbid76
Nov 14 '18 at 19:22
I did, sorry forgot to mention it in post
– Makogan
Nov 14 '18 at 19:40
What aboutf_position = t_position[0]*gl_TessCoord.x + t_position[1]*gl_TessCoord.y + t_position[2]*gl_TessCoord.z;
– Rabbid76
Nov 14 '18 at 19:51
Still no output
– Makogan
Nov 14 '18 at 19:54
1
@Makong At triangle tessellationgl_TessCoordcontains the Barycentric coordinate of the tessellated position on the triangle. You have to define how the new vertex coordinate is calculated. See Tessellation - Triangles.
– Rabbid76
Nov 14 '18 at 20:16
|
show 2 more comments
I am trying to use the tessellation shaders in OpenGL ES 3.2, and have tried to follow 2 different tutorials without success.
I am currently drawing a flat rectangle, the goal is to elevate its surface. I receive the vertices in the vertex shader:
#version 320 es
layout (location = 0) in vec3 position;
out vec3 v_position;
uniform mat4 model_matrix;
uniform mat4 mvp_matrix;
void main() {
vec4 pos = vec4(position, 1.0);
v_position = vec3(model_matrix * pos);
gl_Position = mvp_matrix * vec4(position, 1.0);
}
Attempt to tessellate in the tessellation control shader:
#version 320 es
layout (vertices = 3) out;
in vec3 v_position;
out vec3 t_position;
void main()
{
// Set the control points of the output patch
t_position[gl_InvocationID] = v_position[gl_InvocationID];
// Calculate the tessellation levels
gl_TessLevelOuter[0] = 3.0;
gl_TessLevelOuter[1] = 3.0;
gl_TessLevelOuter[2] = 3.0;
gl_TessLevelInner[0] = gl_TessLevelOuter[2];
}
And then try to make a minimum working evaluation shader:
#version 320 es
layout(triangles, equal_spacing, ccw) in;
in vec3 t_position;
out vec3 f_position;
uniform mat4 mvp_matrix;
void main() {
f_position = t_position[0];
gl_Position = mvp_matrix * vec4(f_position, 1.0);
}
I call these shaders using glDrawArrays(GL_PATCHES, 0, vertex_num). However currently I see no output when attempting to tessellate. if instead I remove the tessellation shaders and draw with only the vertex and fragment shaders (after tweaking so that they compile). I do see the rectangle mesh, so I am confident the issue is in my shaders.
I am not getting compilation errors, and calling glGetError() reports no error, so it's my logic that I think is wrong.
Edit:
Immediately prior to the draw call I also do:
glPatchParameteri(GL_PATCH_VERTICES, 3);
opengl-es glsl shader tessellation
edited Nov 14 '18 at 19:51
genpfault
42.2k95399
asked Nov 14 '18 at 19:17
MakoganMakogan
1,7841829
I am trying to use the tessellation shaders in OpenGL ES 3.2, and have tried to follow 2 different tutorials without success.
I am currently drawing a flat rectangle, the goal is to elevate its surface. I receive the vertices in the vertex shader:
#version 320 es
layout (location = 0) in vec3 position;
out vec3 v_position;
uniform mat4 model_matrix;
uniform mat4 mvp_matrix;
void main() {
vec4 pos = vec4(position, 1.0);
v_position = vec3(model_matrix * pos);
gl_Position = mvp_matrix * vec4(position, 1.0);
}
Attempt to tessellate in the tessellation control shader:
#version 320 es
layout (vertices = 3) out;
in vec3 v_position;
out vec3 t_position;
void main()
{
// Set the control points of the output patch
t_position[gl_InvocationID] = v_position[gl_InvocationID];
// Calculate the tessellation levels
gl_TessLevelOuter[0] = 3.0;
gl_TessLevelOuter[1] = 3.0;
gl_TessLevelOuter[2] = 3.0;
gl_TessLevelInner[0] = gl_TessLevelOuter[2];
}
And then try to make a minimum working evaluation shader:
#version 320 es
layout(triangles, equal_spacing, ccw) in;
in vec3 t_position;
out vec3 f_position;
uniform mat4 mvp_matrix;
void main() {
f_position = t_position[0];
gl_Position = mvp_matrix * vec4(f_position, 1.0);
}
I call these shaders using glDrawArrays(GL_PATCHES, 0, vertex_num). However currently I see no output when attempting to tessellate. if instead I remove the tessellation shaders and draw with only the vertex and fragment shaders (after tweaking so that they compile). I do see the rectangle mesh, so I am confident the issue is in my shaders.
I am not getting compilation errors, and calling glGetError() reports no error, so it's my logic that I think is wrong.
Edit:
Immediately prior to the draw call I also do:
glPatchParameteri(GL_PATCH_VERTICES, 3);
opengl-es glsl shader tessellation
opengl-es glsl shader tessellation
edited Nov 14 '18 at 19:51
genpfault
42.2k95399
asked Nov 14 '18 at 19:17
MakoganMakogan
1,7841829
edited Nov 14 '18 at 19:51
genpfault
42.2k95399
asked Nov 14 '18 at 19:17
MakoganMakogan
1,7841829
edited Nov 14 '18 at 19:51
genpfault
42.2k95399
edited Nov 14 '18 at 19:51
genpfault
42.2k95399
edited Nov 14 '18 at 19:51
genpfault
42.2k95399
42.2k95399
asked Nov 14 '18 at 19:17
MakoganMakogan
1,7841829
asked Nov 14 '18 at 19:17
MakoganMakogan
1,7841829
asked Nov 14 '18 at 19:17
MakoganMakogan
1,7841829
1,7841829
You have to setglPatchParameteri( GL_PATCH_VERTICES, 3 )before the draw call.
– Rabbid76
Nov 14 '18 at 19:22
I did, sorry forgot to mention it in post
– Makogan
Nov 14 '18 at 19:40
What aboutf_position = t_position[0]*gl_TessCoord.x + t_position[1]*gl_TessCoord.y + t_position[2]*gl_TessCoord.z;
– Rabbid76
Nov 14 '18 at 19:51
Still no output
– Makogan
Nov 14 '18 at 19:54
1
@Makong At triangle tessellationgl_TessCoordcontains the Barycentric coordinate of the tessellated position on the triangle. You have to define how the new vertex coordinate is calculated. See Tessellation - Triangles.
– Rabbid76
Nov 14 '18 at 20:16
|
show 2 more comments
You have to setglPatchParameteri( GL_PATCH_VERTICES, 3 )before the draw call.
– Rabbid76
Nov 14 '18 at 19:22
I did, sorry forgot to mention it in post
– Makogan
Nov 14 '18 at 19:40
What aboutf_position = t_position[0]*gl_TessCoord.x + t_position[1]*gl_TessCoord.y + t_position[2]*gl_TessCoord.z;
– Rabbid76
Nov 14 '18 at 19:51
Still no output
– Makogan
Nov 14 '18 at 19:54
1
@Makong At triangle tessellationgl_TessCoordcontains the Barycentric coordinate of the tessellated position on the triangle. You have to define how the new vertex coordinate is calculated. See Tessellation - Triangles.
– Rabbid76
Nov 14 '18 at 20:16
You have to set
glPatchParameteri( GL_PATCH_VERTICES, 3 ) before the draw call.– Rabbid76
Nov 14 '18 at 19:22
You have to set
glPatchParameteri( GL_PATCH_VERTICES, 3 ) before the draw call.– Rabbid76
Nov 14 '18 at 19:22
I did, sorry forgot to mention it in post
– Makogan
Nov 14 '18 at 19:40
I did, sorry forgot to mention it in post
– Makogan
Nov 14 '18 at 19:40
What about
f_position = t_position[0]*gl_TessCoord.x + t_position[1]*gl_TessCoord.y + t_position[2]*gl_TessCoord.z;– Rabbid76
Nov 14 '18 at 19:51
What about
f_position = t_position[0]*gl_TessCoord.x + t_position[1]*gl_TessCoord.y + t_position[2]*gl_TessCoord.z;– Rabbid76
Nov 14 '18 at 19:51
Still no output
– Makogan
Nov 14 '18 at 19:54
Still no output
– Makogan
Nov 14 '18 at 19:54
1
1
@Makong At triangle tessellation
gl_TessCoord contains the Barycentric coordinate of the tessellated position on the triangle. You have to define how the new vertex coordinate is calculated. See Tessellation - Triangles.– Rabbid76
Nov 14 '18 at 20:16
@Makong At triangle tessellation
gl_TessCoord contains the Barycentric coordinate of the tessellated position on the triangle. You have to define how the new vertex coordinate is calculated. See Tessellation - Triangles.– Rabbid76
Nov 14 '18 at 20:16
|
show 2 more comments
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You have to set
glPatchParameteri( GL_PATCH_VERTICES, 3 )before the draw call.– Rabbid76
Nov 14 '18 at 19:22
I did, sorry forgot to mention it in post
– Makogan
Nov 14 '18 at 19:40
What about
f_position = t_position[0]*gl_TessCoord.x + t_position[1]*gl_TessCoord.y + t_position[2]*gl_TessCoord.z;– Rabbid76
Nov 14 '18 at 19:51
Still no output
– Makogan
Nov 14 '18 at 19:54
1
@Makong At triangle tessellation
gl_TessCoordcontains the Barycentric coordinate of the tessellated position on the triangle. You have to define how the new vertex coordinate is calculated. See Tessellation - Triangles.– Rabbid76
Nov 14 '18 at 20:16