View or perspective matrices messing with culling
I have this code here that almost works fine, but it is culling the front faces instead of the back faces:
auto scaleMatrix = glm::scale(glm::mat4(1.0f), glm::fvec3(0.5f, 0.5f, 0.5f));
auto rotateMatrix = glm::rotate(glm::mat4(1.0f), glm::degrees(rotation), glm::fvec3{.0f, 1.f, 0.f});
auto modelMatrix = rotateMatrix * scaleMatrix;
int w, h;
glfwGetWindowSize(window, &w, &h);
auto perspectiveMatrix = glm::perspective(90.f, w/(float)h, .1f, 100.f);
auto viewMatrix = glm::lookAt(
glm::vec3(-1, 0, -1),
glm::vec3(0, 0, 0),
glm::vec3(0, 1, 0)
);
auto mvp = perspectiveMatrix * viewMatrix * modelMatrix;
glUniformMatrix4fv(gMVPLocation, 1, GL_FALSE, &mvp[0][0]);
If I only pass the model matrix to the shader, the correct faces cull. But if I am passing the MVP matrix, the front faces are culled while the back faces are rendered. Not sure why this would cause this issue, but my vertices are defined in ccw winding order and work perfectly fine if I don't use a view or perspective matrix. I'm clueless as to why this doesn't work here.
c++ opengl glfw
asked Nov 22 at 18:17
Potato
264
add a comment |
I have this code here that almost works fine, but it is culling the front faces instead of the back faces:
auto scaleMatrix = glm::scale(glm::mat4(1.0f), glm::fvec3(0.5f, 0.5f, 0.5f));
auto rotateMatrix = glm::rotate(glm::mat4(1.0f), glm::degrees(rotation), glm::fvec3{.0f, 1.f, 0.f});
auto modelMatrix = rotateMatrix * scaleMatrix;
int w, h;
glfwGetWindowSize(window, &w, &h);
auto perspectiveMatrix = glm::perspective(90.f, w/(float)h, .1f, 100.f);
auto viewMatrix = glm::lookAt(
glm::vec3(-1, 0, -1),
glm::vec3(0, 0, 0),
glm::vec3(0, 1, 0)
);
auto mvp = perspectiveMatrix * viewMatrix * modelMatrix;
glUniformMatrix4fv(gMVPLocation, 1, GL_FALSE, &mvp[0][0]);
If I only pass the model matrix to the shader, the correct faces cull. But if I am passing the MVP matrix, the front faces are culled while the back faces are rendered. Not sure why this would cause this issue, but my vertices are defined in ccw winding order and work perfectly fine if I don't use a view or perspective matrix. I'm clueless as to why this doesn't work here.
c++ opengl glfw
asked Nov 22 at 18:17
Potato
264
You should visualize in your mind (or paper) where a triangle is (its coordinates) after scaling & rotating, as seen from the camera you set withlookAt. I guess you'll see the back-face. Notice z-coord will be < 0.
– Ripi2
Nov 22 at 19:26
add a comment |
I have this code here that almost works fine, but it is culling the front faces instead of the back faces:
auto scaleMatrix = glm::scale(glm::mat4(1.0f), glm::fvec3(0.5f, 0.5f, 0.5f));
auto rotateMatrix = glm::rotate(glm::mat4(1.0f), glm::degrees(rotation), glm::fvec3{.0f, 1.f, 0.f});
auto modelMatrix = rotateMatrix * scaleMatrix;
int w, h;
glfwGetWindowSize(window, &w, &h);
auto perspectiveMatrix = glm::perspective(90.f, w/(float)h, .1f, 100.f);
auto viewMatrix = glm::lookAt(
glm::vec3(-1, 0, -1),
glm::vec3(0, 0, 0),
glm::vec3(0, 1, 0)
);
auto mvp = perspectiveMatrix * viewMatrix * modelMatrix;
glUniformMatrix4fv(gMVPLocation, 1, GL_FALSE, &mvp[0][0]);
If I only pass the model matrix to the shader, the correct faces cull. But if I am passing the MVP matrix, the front faces are culled while the back faces are rendered. Not sure why this would cause this issue, but my vertices are defined in ccw winding order and work perfectly fine if I don't use a view or perspective matrix. I'm clueless as to why this doesn't work here.
c++ opengl glfw
asked Nov 22 at 18:17
Potato
264
I have this code here that almost works fine, but it is culling the front faces instead of the back faces:
auto scaleMatrix = glm::scale(glm::mat4(1.0f), glm::fvec3(0.5f, 0.5f, 0.5f));
auto rotateMatrix = glm::rotate(glm::mat4(1.0f), glm::degrees(rotation), glm::fvec3{.0f, 1.f, 0.f});
auto modelMatrix = rotateMatrix * scaleMatrix;
int w, h;
glfwGetWindowSize(window, &w, &h);
auto perspectiveMatrix = glm::perspective(90.f, w/(float)h, .1f, 100.f);
auto viewMatrix = glm::lookAt(
glm::vec3(-1, 0, -1),
glm::vec3(0, 0, 0),
glm::vec3(0, 1, 0)
);
auto mvp = perspectiveMatrix * viewMatrix * modelMatrix;
glUniformMatrix4fv(gMVPLocation, 1, GL_FALSE, &mvp[0][0]);
If I only pass the model matrix to the shader, the correct faces cull. But if I am passing the MVP matrix, the front faces are culled while the back faces are rendered. Not sure why this would cause this issue, but my vertices are defined in ccw winding order and work perfectly fine if I don't use a view or perspective matrix. I'm clueless as to why this doesn't work here.
c++ opengl glfw
c++ opengl glfw
asked Nov 22 at 18:17
Potato
264
asked Nov 22 at 18:17
Potato
264
asked Nov 22 at 18:17
Potato
264
asked Nov 22 at 18:17
Potato
264
asked Nov 22 at 18:17
Potato
264
264
You should visualize in your mind (or paper) where a triangle is (its coordinates) after scaling & rotating, as seen from the camera you set withlookAt. I guess you'll see the back-face. Notice z-coord will be < 0.
– Ripi2
Nov 22 at 19:26
add a comment |
You should visualize in your mind (or paper) where a triangle is (its coordinates) after scaling & rotating, as seen from the camera you set withlookAt. I guess you'll see the back-face. Notice z-coord will be < 0.
– Ripi2
Nov 22 at 19:26
You should visualize in your mind (or paper) where a triangle is (its coordinates) after scaling & rotating, as seen from the camera you set with
lookAt. I guess you'll see the back-face. Notice z-coord will be < 0.– Ripi2
Nov 22 at 19:26
You should visualize in your mind (or paper) where a triangle is (its coordinates) after scaling & rotating, as seen from the camera you set with
lookAt. I guess you'll see the back-face. Notice z-coord will be < 0.– Ripi2
Nov 22 at 19:26
add a comment |
1 Answer
1
active
oldest
votes
When you don't have any transforms (i.e., you supply coordinates directly in clip space) and a standard depth buffer, you have a left-handed coordinate system where the z-axis points away from the viewer. By applying a model matrix with positive determinant (like rotations or positive scalings), you do not change the orientation.
If you use the view-projection matrix from glm, you have a right-handed coordinate system where the z-axis points towards the viewer. Hence, your model will revert its orientation. To solve the problem, either revert the orientation of your faces or set the direction of your front sides using glFrontFace.
answered Nov 22 at 18:35
Nico Schertler
25.1k42350
Just had my z coords of my model wrong, didn't realize -z is away from camera and was storing vertices as if further away was +z.
– Potato
Nov 22 at 21:33
add a comment |
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1 Answer
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1 Answer
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active
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oldest
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oldest
votes
When you don't have any transforms (i.e., you supply coordinates directly in clip space) and a standard depth buffer, you have a left-handed coordinate system where the z-axis points away from the viewer. By applying a model matrix with positive determinant (like rotations or positive scalings), you do not change the orientation.
If you use the view-projection matrix from glm, you have a right-handed coordinate system where the z-axis points towards the viewer. Hence, your model will revert its orientation. To solve the problem, either revert the orientation of your faces or set the direction of your front sides using glFrontFace.
answered Nov 22 at 18:35
Nico Schertler
25.1k42350
Just had my z coords of my model wrong, didn't realize -z is away from camera and was storing vertices as if further away was +z.
– Potato
Nov 22 at 21:33
add a comment |
When you don't have any transforms (i.e., you supply coordinates directly in clip space) and a standard depth buffer, you have a left-handed coordinate system where the z-axis points away from the viewer. By applying a model matrix with positive determinant (like rotations or positive scalings), you do not change the orientation.
If you use the view-projection matrix from glm, you have a right-handed coordinate system where the z-axis points towards the viewer. Hence, your model will revert its orientation. To solve the problem, either revert the orientation of your faces or set the direction of your front sides using glFrontFace.
answered Nov 22 at 18:35
Nico Schertler
25.1k42350
Just had my z coords of my model wrong, didn't realize -z is away from camera and was storing vertices as if further away was +z.
– Potato
Nov 22 at 21:33
add a comment |
When you don't have any transforms (i.e., you supply coordinates directly in clip space) and a standard depth buffer, you have a left-handed coordinate system where the z-axis points away from the viewer. By applying a model matrix with positive determinant (like rotations or positive scalings), you do not change the orientation.
If you use the view-projection matrix from glm, you have a right-handed coordinate system where the z-axis points towards the viewer. Hence, your model will revert its orientation. To solve the problem, either revert the orientation of your faces or set the direction of your front sides using glFrontFace.
answered Nov 22 at 18:35
Nico Schertler
25.1k42350
When you don't have any transforms (i.e., you supply coordinates directly in clip space) and a standard depth buffer, you have a left-handed coordinate system where the z-axis points away from the viewer. By applying a model matrix with positive determinant (like rotations or positive scalings), you do not change the orientation.
If you use the view-projection matrix from glm, you have a right-handed coordinate system where the z-axis points towards the viewer. Hence, your model will revert its orientation. To solve the problem, either revert the orientation of your faces or set the direction of your front sides using glFrontFace.
answered Nov 22 at 18:35
Nico Schertler
25.1k42350
answered Nov 22 at 18:35
Nico Schertler
25.1k42350
answered Nov 22 at 18:35
Nico Schertler
25.1k42350
answered Nov 22 at 18:35
Nico Schertler
25.1k42350
25.1k42350
Just had my z coords of my model wrong, didn't realize -z is away from camera and was storing vertices as if further away was +z.
– Potato
Nov 22 at 21:33
add a comment |
Just had my z coords of my model wrong, didn't realize -z is away from camera and was storing vertices as if further away was +z.
– Potato
Nov 22 at 21:33
Just had my z coords of my model wrong, didn't realize -z is away from camera and was storing vertices as if further away was +z.
– Potato
Nov 22 at 21:33
Just had my z coords of my model wrong, didn't realize -z is away from camera and was storing vertices as if further away was +z.
– Potato
Nov 22 at 21:33
add a comment |
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You should visualize in your mind (or paper) where a triangle is (its coordinates) after scaling & rotating, as seen from the camera you set with
lookAt. I guess you'll see the back-face. Notice z-coord will be < 0.– Ripi2
Nov 22 at 19:26