Questions tagged [projection-matrix]

The tag has no usage guidance.

66 questions
Filter by
Sorted by
Tagged with
110 views

Setting up perspective projection in OpenGL

I'm trying to set up perspective projection in OpenGL but it doesn't work ...
• 11
49 views

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 ...
• 121
1 vote
45 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 ...
• 121
362 views

How do I create a localtoworldmatrix and worldtolocalmatrix in Godot?

From what I can tell Godot uses Projection for 4x4 matrixes, but I see no way to generate a localtoworldmatrix from a given transform in Godot, how do I do this?
• 145
96 views

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
590 views

glm::frustum vs glm::perspectiveFov

When I use glm::perspectiveFov(90.0f,512.0f,512.0f,1.0f,256.0f) I receive a working perspective projection with 90° in both x and y, as seen below (camera is in ...
• 761
43 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 ...
• 139
1 vote
299 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
2k views

When moving the "camera" should one move the projection matrix or move the world?

I'm making my own game engine as an exercise and I've gotten really confused with what I've read so far. When I want to move my camera do I simply just move the world or move the position of the ...
• 103
35 views

How are transformation matrices usually represented?

I know the bare minimum to do matrix multiplication and have implemented them from scratch a few times for various purposes, but every time I do, I make sure to be very clear to myself about where are ...
280 views

How to visualize angle of projection in Oblique Parallel Projection?

We know that in Oblique Parallel Projection Point (x,y,z) is projected to position (x_p,y_p) on the view plane.Projector (oblique) from (x,y,z) to (x_p,y_p) makes an angle alpha. with the line (L) on ...
• 117
1 vote
297 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
5k views

How does glm::lookAt produce a View Matrix?

Say we do this: glm::mat4 View = glm::lookAt(glm::vec3(4,3,-3), glm::vec3(0,0,0),glm::vec3(0,1,0)); And after printing to the console with glm tostring (column ...
• 61
1 vote
230 views

Can I get world-space z-near-plane vertices from projection matrix + z-near distance?

I'm trying to port ShaderToy VR shaders to WebXR (the new browser API for AR/VR devices). ShaderToy VR shaders expect two extra parameters: ray origin (view translation) and ray direction (unit vector ...
• 1,935
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 ...
• 21
415 views

Texture flipping behaviour

I was having this problem with OpenGL where I'd have all my textures being rendered upside down. I did the most logical thing I could think of and tried reversing the order of the mapping and that ...
1 vote
91 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
357 views

Combining cylindrical Billboarding and aligning with velocity (unity)

I'm trying to make a custom GPU particle solution on Unity to fullfill some needs on my project, using compute shaders and custom shader + Graphics.DrawProceduralNow() to draw them. While I managed ...
78 views

Confused about why my projection matrix works

My projection matrix was buggy, I'm not great at mathematics, but I checked it against the the songho tutorial, and the broken one seems correct to me but switching nearplane to farplane seems to ...
• 301
2k views

How does a game like Enter the Gungeon handle forward and backwards movement with their orthographic set up?

So I've been scratching my head at this problem for over a week now, and would love some insight from anyone who might know a bit more. In my game I have the floor flat on the X/Z plane with walls/...
• 131
992 views

How to set the camera projection matrix so that its 4 rays always exactly hit the corners of a defined rectangle?

I have a camera, and I have a rectangle drawn in an arbitrary plane. I need to change the projection matrix of the camera so that the rays along the edges of the camera's frustum always hit the ...
• 1,460
1 vote
82 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
152 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
621 views

OpenGL frustum extraction

I'm trying to extract frustum planes from the camera. The algorithm is simple: create clip to world space matrix (inversed projection * inversed view) multiply clip point by clip to world matrix ...
• 118
971 views

How to set ortho projection / model view matrix without a camera?

I'm trying to create the correct projection and model view matrix for rendering without a camera. _orthoCamera is a camera I set up in the scene view. Using the <...
• 11
1k views

What exactly does XMMatrixPerspective{L,R}H do?

There are generally three functions to create a perspective matrix in DirectXMath, XMMatrixPerspective{L,R}H, ...
• 1,860
211 views

Perspective projection matrix with a non-orthogonal near plane

I'm trying to figure out a way to provide such a perspective projection matrix to a shader that the "near" plane wouldn't necessarily be orthogonal to the camera vector. More specifically, I'm ...
473 views

OpenGL orthographic projection rendering quarter of screen

I'm trying to set up an orthographic projection so I can draw a rectangle using screen coordinates, but even if I draw a rectangle using the width/height of the window, it only fills a quarter of the ...
1 vote
4k views

From screen space to world space for a 2D game

I'm making a 2D game and I want the user to be able to position an object in the world using mouse input. After a while I found an answer to 'OpenGL Math - Projecting Screen space to World space ...
• 113
189 views

How to keep an object in a certain part of the camera view?

I have a 3d camera that is viewing a character that is moving. As the character is moving i want the camera to adjust itself so as to keep the character in the left third of the camera view. I ...
• 101
68 views

Why are the vertices from a mesh not transforming using a camera?

I am able to use a camera class to change the view and rotation of a simple quad, so I know it works, but when I move on to a more advanced geometry, such as a mesh, I am unable to affect the ...
• 105
1 vote
2k views

libGDX - orthographic camera and world units

I've followed the advice in this post to handle world/screen coordinates, but I'm getting results I don't quite understand, as I'm not terribly good in math. So, when I use this code: ...
• 125
1 vote
462 views

set zfar/znear in openGL using shaders (QT env)

I have a QT canvas and I'm using shaders to build my scence. I've set the camera image plane at some position, and would like to view object from the image plane to infinity. How do I set the zfar and ...
• 111
5k views

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
322 views

What are some standard mathematical tests for projection matrices?

I'm trying to double check my math in my projection matrices. I'm thinking about "unit tests" when I ask this. I'm looking for 4 or 5 unit tests that would be appropriate to give one confidence that ...
• 209
690 views

Problem calculating screen point for a point in a 3D world with view matrix and projection matrix

I am trying to calculate the 2D screen point of a 3D world position. For this I use the multiplication ViewMatrix * ProjectionMatrix. But I am not getting good ...
• 121
155 views

How to clip cut-off using different frustrum than that of original camera? How to cut plane by pyramid shape?

SOURCE : http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2012/10/Mitchell_LightShafts.pdf This process is part of creating light draft effect. And I am suggested to do the described process in ...
• 1,112
162 views

OpenGL Perspective Issue

I'm trying to troubleshoot a problem with my simple OpenGL test program, which I've written in C. I've written some math routines to do the matrix manipulation, but even after copying known working ...
• 151
2k views

360 degree video of my OpenGL game

I want to make a 360 degree video of my OpenGL game. Concerning the rendering: Is it enough to render it in OpenGL with a specific projection matrix? If yes, which one? Or can I render it into a cube ...
• 91
1 vote
59 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 ...
5k views

libGDX - Why do I have to use camera.setToOrtho what does it do?

I am very confused about camera matrices and I don't know where to start my studying. Maybe I have to study OpenGL, but I don't know C++ ... Ok so I have a camera, Box2d world and a Box2d body. <...
• 193
2k views

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
104 views

2D World Mouse Coordinates - Matrices

I'm trying to get the world coordinates out of a mouse click. Currently I'm doing the following: ...
265 views

Calculate camera target

How calculate camera target position, if I have front/back planes, camera transformation matrix and camera lens length?
1k views

Project camera-to-pixel ray in world coordinates

I'm trying to implement a very simple ray tracing function but I have a problem with projecting the camera ray (from camera to pixel) to the world space. In the screen coordinates have the pixel ...
• 99
107 views

Does a Standard Exist for Game Entity View Frustums

I was just recently adding the ability for my in-game entities to have their own Frustums, with the intentions of making them able to see enemies later down the road of my development cycle. My custom ...
• 790
649 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
1 vote
112 views

What are projection independent ways of determining whether a normal is facing the viewer?

A position v and normal n are given in world coordinates. Also there is a view matrix V for ...
246 views

Projection Matrix Breaks My Rectangle

This is my vertex shader, shown below. ...
• 1,176
1 vote