# Questions tagged [projection-matrix]

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18 questions with no upvoted or accepted answers
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### Deproject Screen To World Coordinates (Unreal Engine 4.15)

I am working on a small game in Unreal Engine 4.15 using blueprints only and encountered a behaviour I don't understand. The game is based on the Top Down Example. As I'd like to teleport an actor ...
• 31
642 views

### Control frustum near and far clip plane sizes in a Projection Matrix

I'm trying to achieve a dolly zoom effect. My first try was the obvious one, the original "zoom in & dolly out" technique, which works nicely. Except that there are cases which this is not ...
• 389
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### How to correctly rotate 2D orthographic projection around a central point?

I want to rotate a 2D orthographic projection around the centre point of my view. However, something is off (it looks like a translation) but I'm not sure what. To put some concrete values on the ...
• 123
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### How to achieve the top-down (oblique) projection of textures using an OrthographicCamera?

This question is related to (How to calculate the initial velocity of projectile motion by a given distance and angle from point A to B) question. Details In the below image is the graphical ...
• 501
1 vote
44 views

### How to Generate a Texture to Make an Obstructing Plane Appear Invisible in a 3D Scene?

I have a 3D scene with a camera. Between the camera and the scene, I have a plane with arbitrary orientation. This plane obscures a portion of the scene from the camera’s perspective (anything behind ...
• 111
1 vote
180 views

### In a 3D projection, how to find 'w' for every y point on the screen

I have a standard 3D rendering pipeline. Let's say I have a camera looking down at a flat plane that represents the floor. (in my game, z = height, so this is a plane where z == 0), and for ...
• 181
1 vote
288 views

### How to get world coordinates from a 4X4 camera matrix

I have Intel T265 camera which has a camera coordinates system like following diagram: The camera system has two cameras and the center of the two cameras is the position of the camera system. The ...
• 111
1 vote
81 views

### My triangle disappears when multiplaying by my perspective projection matrix

Whenever I multiply my transformation matrix, which is passed to the shader via constant buffer, my triangle disappears. Here is the code for the passed matrix: ...
1 vote
78 views

### Why projection window is between -1 and 1

Is it a convetion ? What we achieve with this ? I am reading about how the perspective and orthographic matrix is getting calculated and everyone is trying to normalize the homogenous coordinates to [...
• 11
1 vote
131 views

### How and where to transform a Camera Frustum onto a tilted screen?

In rendering tutorials for perspective projection the assumption is that the rendering surface is perpendicular to the sight line. As shown here: How to accommodate for a screen that is tilted ...
• 185
1 vote
57 views

### Convert box to matrix

I have a box (non-rectangular cuboid?) and would like to convert it to a matrix such that when a point inside the box is multiplied by the matrix, a vector is returned that describes the relative ...
1 vote
1k views

### How can I get shadows to appear correctly when using a custom projection matrix?

EDIT: This has been officially marked as a bug in Unity. If anyone else has this issue, you can vote here for Unity to fix it. As mentioned in this thread, I'm using a custom projection matrix in ...
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### Setting up perspective projection in OpenGL

I'm trying to set up perspective projection in OpenGL but it doesn't work ...
• 11
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### How to obtain the Position on the screen (Vector2) of the Position of an object in the world (Vector3)?

I have been searching around for a solution to this but still haven't been able to use it or find it, the thing is i need the Screen Position of an object that is being seen, for this i have three ...
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37 views

### Is directional shadow mapping without projection matrix possible?

I have found this code where they use a cubemap for pointlight shadow and they don't need to retrieve the faceindex and the projection matrix. This greatly improve the FPS. I was wondering if this ...
• 129
44 views

### NDK opengl-es unknown error

Projection matrix? Renderer? Where is the error? I recently started studying NDK to create better performing android games ... but ... An error I didn't expect to deal with appeared a few weeks ago ...
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