OpenGL ray tracing using inverse transformations
I have a pipeline that uses model, view and projection matrices to render a triangle mesh.
I am trying to implement a ray tracer that will pick out the object I'm clicking on by projecting the ray origin and direction by the inverse of the transformations.
When I just had a model (no view or projection) in the vertex shader I had
Vector4f ray_origin = model.inverse() * Vector4f(xworld, yworld, 0, 1);
Vector4f ray_direction = model.inverse() * Vector4f(0, 0, -1, 0);
and everything worked perfectly. However, I added a view and projection matrix and then changed the code to be
Vector4f ray_origin = model.inverse() * view.inverse() * projection.inverse() * Vector4f(xworld, yworld, 0, 1);
Vector4f ray_direction = model.inverse() * view.inverse() * projection.inverse() * Vector4f(0, 0, -1, 0);
and nothing is working anymore. What am I doing wrong?
c++ opengl raytracing
edited Nov 25 '18 at 15:31
Rabbid76
36.2k113247
asked Nov 25 '18 at 11:42
LivingRobotLivingRobot
367620
add a comment |
I have a pipeline that uses model, view and projection matrices to render a triangle mesh.
I am trying to implement a ray tracer that will pick out the object I'm clicking on by projecting the ray origin and direction by the inverse of the transformations.
When I just had a model (no view or projection) in the vertex shader I had
Vector4f ray_origin = model.inverse() * Vector4f(xworld, yworld, 0, 1);
Vector4f ray_direction = model.inverse() * Vector4f(0, 0, -1, 0);
and everything worked perfectly. However, I added a view and projection matrix and then changed the code to be
Vector4f ray_origin = model.inverse() * view.inverse() * projection.inverse() * Vector4f(xworld, yworld, 0, 1);
Vector4f ray_direction = model.inverse() * view.inverse() * projection.inverse() * Vector4f(0, 0, -1, 0);
and nothing is working anymore. What am I doing wrong?
c++ opengl raytracing
edited Nov 25 '18 at 15:31
Rabbid76
36.2k113247
asked Nov 25 '18 at 11:42
LivingRobotLivingRobot
367620
add a comment |
I have a pipeline that uses model, view and projection matrices to render a triangle mesh.
I am trying to implement a ray tracer that will pick out the object I'm clicking on by projecting the ray origin and direction by the inverse of the transformations.
When I just had a model (no view or projection) in the vertex shader I had
Vector4f ray_origin = model.inverse() * Vector4f(xworld, yworld, 0, 1);
Vector4f ray_direction = model.inverse() * Vector4f(0, 0, -1, 0);
and everything worked perfectly. However, I added a view and projection matrix and then changed the code to be
Vector4f ray_origin = model.inverse() * view.inverse() * projection.inverse() * Vector4f(xworld, yworld, 0, 1);
Vector4f ray_direction = model.inverse() * view.inverse() * projection.inverse() * Vector4f(0, 0, -1, 0);
and nothing is working anymore. What am I doing wrong?
c++ opengl raytracing
edited Nov 25 '18 at 15:31
Rabbid76
36.2k113247
asked Nov 25 '18 at 11:42
LivingRobotLivingRobot
367620
I have a pipeline that uses model, view and projection matrices to render a triangle mesh.
I am trying to implement a ray tracer that will pick out the object I'm clicking on by projecting the ray origin and direction by the inverse of the transformations.
When I just had a model (no view or projection) in the vertex shader I had
Vector4f ray_origin = model.inverse() * Vector4f(xworld, yworld, 0, 1);
Vector4f ray_direction = model.inverse() * Vector4f(0, 0, -1, 0);
and everything worked perfectly. However, I added a view and projection matrix and then changed the code to be
Vector4f ray_origin = model.inverse() * view.inverse() * projection.inverse() * Vector4f(xworld, yworld, 0, 1);
Vector4f ray_direction = model.inverse() * view.inverse() * projection.inverse() * Vector4f(0, 0, -1, 0);
and nothing is working anymore. What am I doing wrong?
c++ opengl raytracing
c++ opengl raytracing
edited Nov 25 '18 at 15:31
Rabbid76
36.2k113247
asked Nov 25 '18 at 11:42
LivingRobotLivingRobot
367620
edited Nov 25 '18 at 15:31
Rabbid76
36.2k113247
asked Nov 25 '18 at 11:42
LivingRobotLivingRobot
367620
edited Nov 25 '18 at 15:31
Rabbid76
36.2k113247
edited Nov 25 '18 at 15:31
Rabbid76
36.2k113247
edited Nov 25 '18 at 15:31
Rabbid76
36.2k113247
36.2k113247
asked Nov 25 '18 at 11:42
LivingRobotLivingRobot
367620
asked Nov 25 '18 at 11:42
LivingRobotLivingRobot
367620
asked Nov 25 '18 at 11:42
LivingRobotLivingRobot
367620
367620
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
If you use perspective projection, then I recommend to define the ray by a point on the near plane and another one on the far plane, in normalized device space. The z coordinate of the near plane is -1 and the z coordinate of the far plane 1. The x and y coordinate have to be the "click" position on the screen in the range [-1, 1] The coordinate of the bottom left is (-1, -1) and the coordinate of the top right is (1, 1). The window or mouse coordinates can be mapped linear to the NDCs x and y coordinates:
float x_ndc = 2.0 * mouse_x/window_width - 1.0;
flaot y_ndc = 1.0 - 2.0 * mouse_y/window_height; // flipped
Vector4f p_near_ndc = Vector4f(x_ndc, y_ndc, -1, 1); // z near = -1
Vector4f p_far_ndc = Vector4f(x_ndc, y_ndc, 1, 1); // z far = 1
A point in normalized device space can be transformed to model space by the inverse projection matrix, then the inverse view matrix and finally the inverse model matrix:
Vector4f p_near_h = model.inverse() * view.inverse() * projection.inverse() * p_near_ndc;
Vector4f p_far_h = model.inverse() * view.inverse() * projection.inverse() * p_far_ndc;
After this the point is a Homogeneous coordinates, which can be transformed by a Perspective divide to a Cartesian coordinate:
Vector3f p0 = p_near_h.head<3>() / p_near_h.w();
Vector3f p1 = p_far_h.head<3>() / p_far_h.w();
The "ray" in model space, defined by point r and a normalized direction d finally is:
Vector3f r = p0;
Vector3f d = (p1 - p0).normalized()
answered Nov 25 '18 at 15:30
Rabbid76Rabbid76
36.2k113247
I'm trying this and still not quite intersecting. It seems to be off by quite a large factor as the ray_origin is all > 1, when previously it was all between 0 and 1.
– LivingRobot
Nov 27 '18 at 1:42
add a comment |
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1 Answer
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
If you use perspective projection, then I recommend to define the ray by a point on the near plane and another one on the far plane, in normalized device space. The z coordinate of the near plane is -1 and the z coordinate of the far plane 1. The x and y coordinate have to be the "click" position on the screen in the range [-1, 1] The coordinate of the bottom left is (-1, -1) and the coordinate of the top right is (1, 1). The window or mouse coordinates can be mapped linear to the NDCs x and y coordinates:
float x_ndc = 2.0 * mouse_x/window_width - 1.0;
flaot y_ndc = 1.0 - 2.0 * mouse_y/window_height; // flipped
Vector4f p_near_ndc = Vector4f(x_ndc, y_ndc, -1, 1); // z near = -1
Vector4f p_far_ndc = Vector4f(x_ndc, y_ndc, 1, 1); // z far = 1
A point in normalized device space can be transformed to model space by the inverse projection matrix, then the inverse view matrix and finally the inverse model matrix:
Vector4f p_near_h = model.inverse() * view.inverse() * projection.inverse() * p_near_ndc;
Vector4f p_far_h = model.inverse() * view.inverse() * projection.inverse() * p_far_ndc;
After this the point is a Homogeneous coordinates, which can be transformed by a Perspective divide to a Cartesian coordinate:
Vector3f p0 = p_near_h.head<3>() / p_near_h.w();
Vector3f p1 = p_far_h.head<3>() / p_far_h.w();
The "ray" in model space, defined by point r and a normalized direction d finally is:
Vector3f r = p0;
Vector3f d = (p1 - p0).normalized()
answered Nov 25 '18 at 15:30
Rabbid76Rabbid76
36.2k113247
I'm trying this and still not quite intersecting. It seems to be off by quite a large factor as the ray_origin is all > 1, when previously it was all between 0 and 1.
– LivingRobot
Nov 27 '18 at 1:42
add a comment |
If you use perspective projection, then I recommend to define the ray by a point on the near plane and another one on the far plane, in normalized device space. The z coordinate of the near plane is -1 and the z coordinate of the far plane 1. The x and y coordinate have to be the "click" position on the screen in the range [-1, 1] The coordinate of the bottom left is (-1, -1) and the coordinate of the top right is (1, 1). The window or mouse coordinates can be mapped linear to the NDCs x and y coordinates:
float x_ndc = 2.0 * mouse_x/window_width - 1.0;
flaot y_ndc = 1.0 - 2.0 * mouse_y/window_height; // flipped
Vector4f p_near_ndc = Vector4f(x_ndc, y_ndc, -1, 1); // z near = -1
Vector4f p_far_ndc = Vector4f(x_ndc, y_ndc, 1, 1); // z far = 1
A point in normalized device space can be transformed to model space by the inverse projection matrix, then the inverse view matrix and finally the inverse model matrix:
Vector4f p_near_h = model.inverse() * view.inverse() * projection.inverse() * p_near_ndc;
Vector4f p_far_h = model.inverse() * view.inverse() * projection.inverse() * p_far_ndc;
After this the point is a Homogeneous coordinates, which can be transformed by a Perspective divide to a Cartesian coordinate:
Vector3f p0 = p_near_h.head<3>() / p_near_h.w();
Vector3f p1 = p_far_h.head<3>() / p_far_h.w();
The "ray" in model space, defined by point r and a normalized direction d finally is:
Vector3f r = p0;
Vector3f d = (p1 - p0).normalized()
answered Nov 25 '18 at 15:30
Rabbid76Rabbid76
36.2k113247
I'm trying this and still not quite intersecting. It seems to be off by quite a large factor as the ray_origin is all > 1, when previously it was all between 0 and 1.
– LivingRobot
Nov 27 '18 at 1:42
add a comment |
If you use perspective projection, then I recommend to define the ray by a point on the near plane and another one on the far plane, in normalized device space. The z coordinate of the near plane is -1 and the z coordinate of the far plane 1. The x and y coordinate have to be the "click" position on the screen in the range [-1, 1] The coordinate of the bottom left is (-1, -1) and the coordinate of the top right is (1, 1). The window or mouse coordinates can be mapped linear to the NDCs x and y coordinates:
float x_ndc = 2.0 * mouse_x/window_width - 1.0;
flaot y_ndc = 1.0 - 2.0 * mouse_y/window_height; // flipped
Vector4f p_near_ndc = Vector4f(x_ndc, y_ndc, -1, 1); // z near = -1
Vector4f p_far_ndc = Vector4f(x_ndc, y_ndc, 1, 1); // z far = 1
A point in normalized device space can be transformed to model space by the inverse projection matrix, then the inverse view matrix and finally the inverse model matrix:
Vector4f p_near_h = model.inverse() * view.inverse() * projection.inverse() * p_near_ndc;
Vector4f p_far_h = model.inverse() * view.inverse() * projection.inverse() * p_far_ndc;
After this the point is a Homogeneous coordinates, which can be transformed by a Perspective divide to a Cartesian coordinate:
Vector3f p0 = p_near_h.head<3>() / p_near_h.w();
Vector3f p1 = p_far_h.head<3>() / p_far_h.w();
The "ray" in model space, defined by point r and a normalized direction d finally is:
Vector3f r = p0;
Vector3f d = (p1 - p0).normalized()
answered Nov 25 '18 at 15:30
Rabbid76Rabbid76
36.2k113247
If you use perspective projection, then I recommend to define the ray by a point on the near plane and another one on the far plane, in normalized device space. The z coordinate of the near plane is -1 and the z coordinate of the far plane 1. The x and y coordinate have to be the "click" position on the screen in the range [-1, 1] The coordinate of the bottom left is (-1, -1) and the coordinate of the top right is (1, 1). The window or mouse coordinates can be mapped linear to the NDCs x and y coordinates:
float x_ndc = 2.0 * mouse_x/window_width - 1.0;
flaot y_ndc = 1.0 - 2.0 * mouse_y/window_height; // flipped
Vector4f p_near_ndc = Vector4f(x_ndc, y_ndc, -1, 1); // z near = -1
Vector4f p_far_ndc = Vector4f(x_ndc, y_ndc, 1, 1); // z far = 1
A point in normalized device space can be transformed to model space by the inverse projection matrix, then the inverse view matrix and finally the inverse model matrix:
Vector4f p_near_h = model.inverse() * view.inverse() * projection.inverse() * p_near_ndc;
Vector4f p_far_h = model.inverse() * view.inverse() * projection.inverse() * p_far_ndc;
After this the point is a Homogeneous coordinates, which can be transformed by a Perspective divide to a Cartesian coordinate:
Vector3f p0 = p_near_h.head<3>() / p_near_h.w();
Vector3f p1 = p_far_h.head<3>() / p_far_h.w();
The "ray" in model space, defined by point r and a normalized direction d finally is:
Vector3f r = p0;
Vector3f d = (p1 - p0).normalized()
answered Nov 25 '18 at 15:30
Rabbid76Rabbid76
36.2k113247
edited Nov 25 '18 at 15:35
answered Nov 25 '18 at 15:30
Rabbid76Rabbid76
36.2k113247
answered Nov 25 '18 at 15:30
Rabbid76Rabbid76
36.2k113247
answered Nov 25 '18 at 15:30
Rabbid76Rabbid76
36.2k113247
36.2k113247
I'm trying this and still not quite intersecting. It seems to be off by quite a large factor as the ray_origin is all > 1, when previously it was all between 0 and 1.
– LivingRobot
Nov 27 '18 at 1:42
add a comment |
I'm trying this and still not quite intersecting. It seems to be off by quite a large factor as the ray_origin is all > 1, when previously it was all between 0 and 1.
– LivingRobot
Nov 27 '18 at 1:42
I'm trying this and still not quite intersecting. It seems to be off by quite a large factor as the ray_origin is all > 1, when previously it was all between 0 and 1.
– LivingRobot
Nov 27 '18 at 1:42
I'm trying this and still not quite intersecting. It seems to be off by quite a large factor as the ray_origin is all > 1, when previously it was all between 0 and 1.
– LivingRobot
Nov 27 '18 at 1:42
add a comment |
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