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Questions about the conversions of a 3D model to a 2D model.
140 questions
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How to select multiple objects in a 3D scene with perspective?
I would like to select multiple object from a rectangle drawn with the mouse. But once unprojected, the rectangle become a trapeze.
These objects are on an inclined plane facing the camera.
The ...
- 101
1
vote
1
answer
39
views
Intersect an Orthographic Shadow Projection with the Visible View Frustum
I'm working on a basic single-projection (not cascaded) shadow map in OpenGl to understand the basics.
I'm converting my world's AABB bounds to light space, calculating the left/right/top/bottom/near/...
- 11
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64
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Projection matrix to Intrinsic parameters
I want to convert a projection matrix in the following form:
$$ {\bf P} :=
\begin{pmatrix}
\frac{f}{a \tan\left(\frac{f}{2}\right)} & 0 & 0 & 0 \\
0 & \frac{f}{\tan\...
- 1
-1
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1
answer
43
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Projecting Vectors (3D to 2D) Using Homogeneous Coordinates, With Known Camera Calibration
Suppose I have vectors in a 3D space (their starting points, dx, dy, and dz), and I would like to project them onto a camera, which I already have as a 3x4 projection matrix.
I can of course project ...
- 1
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1
answer
55
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Transforming UVs from rectangular to azimuthal spherical projection
I'm trying to figure out a general way to project a rectangular texture into a spherical one centered on the azimuth (UN flag style).
As a reference, I have been able to achieve this effect exactly ...
1
vote
2
answers
153
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Is my perspective incorrect?
I am trying to implement a UVN free camera for browsing the 3D space of my OpenGL simulation and I noticed the perspective is introducing some sort of distortion. I observed it is more noticeable ...
- 141
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votes
1
answer
35
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Why does one matrix correctly project points to the plane, but another one doesn't?
I have a scene with a floating cube and a plane y=0. I want to create a simple planar shadow of the cube on the plane. To do this, I just have to project the vertices of the cube to the plane. I can ...
- 101
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1
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66
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Why does Zooming in does not work with Projection Matrix but works in Real Life?
My goal is to project 3D bounding boxes to an image. For those who are not familiar with what 3 Dimensional Bounding Boxes are, they are basically boxes defined by eight corners encapsulating an ...
0
votes
1
answer
61
views
Ray direction in VR (Vision Pro)
I am trying to calculate the ray direction for each pixel in a post processing shader on the Vision Pro for raymarching. I am using the inverse of the projection matrix created from the tangents ...
- 101
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83
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Ocean screen grid projection and animation
I am trying to port the Bruneton Ocean demo to Vulkan and I am having a bit of trouble with the coordinate system. I am using the matrices from the original code but I am not sure what this is doing:
<...
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46
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Name of non-standard perspective projection where parallel lines do not meet at a single vanishing point
I have made a non-standard perspective projection for a rectangular room (see left figure), in which for stylistic reasons, I chose to make the perspective "width" of the walls equal ...
- 1
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1
answer
62
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How are these two projection matrices related?
I have two 3D perspective projection matrices $A,B$ with standard projection parameters $k=\cot(\theta/2)$, where $\theta$ is the field of view, $n$ is the $z$-near value, $f$ is the $z$-far value, ...
- 157
1
vote
1
answer
117
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In perspective projection matrices, why isn't $z_\text{eye}$ mapped linearly to NDC?
As far as my understanding goes, in projection matrices $x_\text{eye}$ and $y_\text{eye}$ are mapped linearly to NDC by first using proportions to find $x_n = \frac{n\cdot x_e}{-z_e}$ and $y_n = \frac{...
3
votes
1
answer
126
views
Formula for cubemap resolution for intended equirectangular resolution
Suppose I want to render out 6 cubemap cameras (90 degree FOV etc.) with the intention of combining them together in post-production into an equirectangular (latlong, 2:1) image.
Suppose I also know ...
- 73
0
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1
answer
22
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viewing direction vectors are not parallel in orthographic projection
I did some math with orthographic projection matrix to compute viewing direction vectors in screen space.
I thought all viewing direction vectors should be parallel in orthographic projection because, ...
- 103