Questions tagged [transformation]

Transformation in game development is usually refers to linear algebra operations on points, vectors and matrices.

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88
votes
9answers
52k views

Why do we move the world instead of the camera?

I heard that in an OpenGL game what we do to let the player move is not to move the camera but to move the whole world around. For example here is an extract of this tutorial: OpenGL View matrix ...
46
votes
2answers
19k views

I'm rotating an object on two axes, so why does it keep twisting around the third axis?

I see questions come up quite often that have this underlying issue, but they're all caught up in the particulars of a given feature or tool. Here's an attempt to create a canonical answer we can ...
26
votes
2answers
5k views

Using Quaternions: What can I do with them? (without the maths)

I am a Game Developer and did not study Mathematics. So I only want to use Quaternions as a tool. And to be able to work with 3D rotation, it's necessary to use Quaternions (Or Matrixes, but let's ...
13
votes
3answers
38k views

How to extract euler angles from transformation matrix?

I have a simple realisation of entity/component game engine. Transform component have methods to set local position, local rotation, global position and global rotation. If transform is being set new ...
13
votes
2answers
10k views

How is the gimbal locked problem solved using accumulative matrix transformations

I am reading the online "Learning Modern 3D Graphics Programming" book by Jason L. McKesson As of now, I am up to the gimbal lock problem and how to solve it using quaternions. However right here, ...
12
votes
2answers
3k views

Why do we need a fourth coordinate to divide by z?

I read the response here: What does the graphics card do with the fourth element of a vector as the final position? "The fourth component is a trick to keep track of perspective projection. When ...
11
votes
1answer
842 views

Special relativity shader in GLSL

I'm trying to implement a GLSL shader which helps understanding special relativity Lorentz Transformation. Let's take two axis-aligned inertial observer O and <...
10
votes
2answers
5k views

How can you extract orientation from a transformation matrix?

I have a 4x4 transformation matrix M, and I want to find out the shape of a sphere when transformed by M. (Sphere is at the origin and has radius 1.) I know I can find the center by just multiplying ...
9
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4answers
3k views

Geometric Transformations on the CPU vs GPU

I've noticed that many 3d programs normally do vector/matrix calculations as well as geometric transformations on the CPU. Has anyone found an advantage in moving these calculations into vertex ...
8
votes
1answer
8k views

How does Mikktspace work for calculating the tangent space during normal mapping?

Increasingly the 3D industry is adopting the standard of Mikktspace for calculating tangent space for normal mapping and other effects which rely on accurate and consistent calculation of tangent ...
8
votes
2answers
2k views

How do I create a draggable object which snaps to obstacles in the way?

I bring yet-another-drag-with-mouse question (I am using Unity with C#), but with a less common particular detail: the existence of obstacles in the middle of the way trough which dragging occurs (3D ...
6
votes
3answers
17k views

Rotate object to always face camera

I'm trying to make a TextMesh appear when ever an enemy prefab is hit. I currently have this functionality working. However, the text doesn't face the direction the players camera is looking. At the ...
6
votes
3answers
870 views

Transforming a primitive tetrahedron into a primitive icosahedron?

I've created a tetrahedron by creating a BoundingBox and building the faces of the tetrahedron within the bounding box as follows (see image as well): ...
6
votes
2answers
2k views

Why translation uses multiplication and not addition? [closed]

To translate an object from (x, y, z) to (a + x, b + y, c + z) it's done using: OK, that's cool, but why would we multiply in ...
6
votes
2answers
5k views

Transform world space using Kinect FloorClipPlane to move origin to floor while keeping orientation

The Kinect SDK provides a property SkeletonFrame.FloorClipPlane that describes the orientation of the floor plane relative to the camera. MSDN contains slightly more information in the Coordinate ...
6
votes
1answer
1k views

How can I attach a model to the bone of another model?

I am trying to attach one animated model to one of the bones of another animated model in an XNA game. I've found a few questions/forum posts/articles online which explain how to attach a weapon ...
6
votes
1answer
420 views

How can I convert OBJ data into CSS3D transformations?

I want to convert the data in a 3D .obj file (vertices, normals, faces) to CSS3D (width, height, rotateX,Y,Z and/or similar transforms). I found a bunch of ...
5
votes
2answers
19k views

How can I stop transform.position from being modified when adding a child object?

I suspect there is a well-known and easy to explain reason for the behavior I'm seeing, but I am having difficulty explaining it (and likely not able to Google for the answer). When adding a child <...
5
votes
3answers
24k views

How do I make a background fill the whole screen in Libgdx?

I'm using this code to set a 800x420 image to be full screen: ...
5
votes
1answer
168 views

What methods can be used to rotate a tiled structure?

I'm trying to rotate some structures that are locked on a grid-like structure. This means I'm looking for lossless ways to rotate the tiles. Maintaining proper distances are not important, I'm aware ...
5
votes
1answer
557 views

How do I deal with floating-point error given a far-away camera?

Whenever a camera is "far" away (its location is some "large" vector), trouble arises when rendering objects close to it: It is the classic precision loss from subtracting 2 floating point numbers. I ...
5
votes
1answer
973 views

Does converting quaternion to matrix cause a lot of overhead?

This is related to rendering creating a model, view, projection matrix for opengl. While matrix are fairly standard there's a lot of talk about using quaternions for rotations but why would u go from ...
5
votes
2answers
989 views

Precision loss when transforming from cartesian to isometric

My goal is to display a tile map in isometric projection. This tile map has 25 tiles across and 25 tiles down. Each tile is 32x32. See below for how I'm accomplishing this. World Space World Space ...
5
votes
1answer
404 views

Are there multiple valid definitions for what translate, rotate and scale do?

Are there multiple valid definitions for what translate, rotate and scale do to the 4x4 matrix? I bring up this question, because I have a simple webgl program that draws a square and does a few ...
5
votes
1answer
852 views

importing animations in Blender, weird rotations/locations

This is for the Blender 2.6 API. There are two problems: 1. When I import a single animation frame from my animation file to Blender, all bones look fine. But when I import multiple (all of the ...
4
votes
3answers
2k views

In Unity, how to get reference of descendant?

I'm trying to get descendant game object, not a child. Let's assume that I have a GameObject and it's hierachy looks like this: ...
4
votes
1answer
380 views

Does vector transformation order matter?

Theoretical question - imagine a car object. There are two (or more) 'forces' acting on this car, these forces will affect where the car will steer. But the forces are calculated using car's location ...
4
votes
1answer
547 views

Do matrix manipulations for 3D graphics ever produce singular matrices?

A singular matrix is a matrix that cannot be inverted. The vecmath library, for example, throws a SingularMatrixException if you try to invert a singular matrix. I think I understand what singular ...
4
votes
1answer
3k views

Is it more efficient to transform vertices on the CPU or the GPU?

Working on optimizing the rendering core of my game engine and I have a couple of questions. Is it more efficient to transform vertices to world space on the CPU before you send then stream to the ...
4
votes
1answer
2k views

How rotate a 3D cube at its center XNA?

I try to rotate a 3D cube on itself from its center, not the edge. Here is my code used. ...
4
votes
1answer
208 views

How to scale major and minor radius of a quarter torus

I am dealing with quarter tori as in the image below. My issue is that I need to be able to scale its major radius and minor radius separately using a scale matrix. However, when I use a regular ...
4
votes
1answer
6k views

Unity C# Object Scaling when parenting by script

How do I make it so an object doesn't scale with another object that I parented it with by script? If anyone knows how to get around this I would really appreciate it. This is the part of the script ...
4
votes
1answer
683 views

How to transform mesh components?

I am attempting to transform the components of a mesh directly using a 4x4 matrix. This is working for the vertex positions, but it is not working for the normals (and probably not the tangents either)...
4
votes
3answers
4k views

Translating an object in the rotation direction

I am creating a graphical scene with OpenGL and SDL, and I'm running into a problem in regards to translating an object in its rotation direction. Each of the graphical objects in the scene has a <...
4
votes
2answers
9k views

Unity / Rotate a point around an arbitrary axis and anchor

I'm trying to find out the point which is already rotated. To solve this I did a Rotation, save the position, set the previous position and return my position, like this: ...
4
votes
0answers
689 views

Shadow mapping - Can't get the right texture coordinates

I'm trying to implement shadow maps for Spotlight's, but alas I can't get them to work. I have verified that my fragment shader is getting the shadow map texture. I can sample from it in the ...
4
votes
1answer
1k views

How to translate swipe gestures into rotations?

I am making a snake game. I want to rotate my snake in the direction specified by swiping on the screen, the directions are limited to orthogonals (90 degree increments). It's an android game. Can ...
3
votes
4answers
2k views

How and when do the model to world, world to view, et cetera multiplications happen?

I learn matrix transformations for game design and I struggle with some basic concepts. I see the actual multiplication taking place before rendering in this sequence: MODEL into WORLD: multiply each ...
3
votes
1answer
37k views

How can I translate a game object towards a position?

I am instantiating my game objects (spheres) through scripts. I want my spheres to move from one location to another. but I don't know how to do this. Update is ...
3
votes
1answer
3k views

LibGDX viewport touch coordinates transformation

I've been trying to get LibGDX's viewport and camera unproject() to work and so far none of the tutorials/answers I've found have worked for me. I have a game window of 840x480 units with FitViewport....
3
votes
2answers
3k views

How can I reflect a point with respect to the plane?

How can I reflect a point with respect to a plane? Example: I have three points (0,0,2), (4,0,0) and (0,8,0). And I have a point (x,y,z). From these, I want derive a composite transformation matrix. ...
3
votes
1answer
7k views

How to mirror/reflect/flip a 4D transformation matrix

I am importing my animation keyframe joint data from Blender to my game engine. The joint data is a set of 4D matrices. Things are looking good except a remaining issue where the animation is facing ...
3
votes
4answers
4k views

(unity) move the world or the character

I'm making a game like this: https://www.youtube.com/watch?v=hO7573lphqI wherein a 3D ship is flying around on a 2D plane. From the player's perspective, the ship will stay stationary in the center ...
3
votes
1answer
183 views

What does the Node2D transform property do?

Following a Godot tutorial I encountered the transform property, but I'm not sure what it means nor how to use it. I read the official Godot documentation, but it ...
3
votes
2answers
431 views

Transform.LookingAt() does nothing

To get used to how Godot transforms work, I am attempting to write an orbit control. The goal is for it to behave similarly to the Godot viewport. So far I have the positioning of my camera working. ...
3
votes
1answer
555 views

what is the very last element of a 4x4 transformation matrix for? [duplicate]

while its a similar value to its neighbour - Z translation (and I wont say if thats above or to the left for fear of sparking a religious war!) and it only seems to change when the Z translation value ...
3
votes
2answers
892 views

Calculating transform of arrow model pointing at some point in 3D space

I'm working on a 3D flight game and I'd like to implement a simple "navigation arrow" pointing at the next waypoint in world which the player has to fly to. I have position of both airplane (=camera) ...
3
votes
1answer
160 views

What is the near plane equation in NDC?

I'm trying to compute the line intersecting my plane (transformed to NDC) and the near plane. I have troubles to get a correct result and I think it is coming from the near plane equation. I ...
3
votes
1answer
2k views

How to project spherical coordinates to canvas

I have objects with coordinates in a spherical coordinate system (altitude alt and azmiuth az). I want to project those to my canvas with a given size (128 x 128 pixels²) and resolution (about 6 px/°)....
3
votes
1answer
2k views

Shear transformation in the projection matrix?

I am trying to understand what the shear transformation (l+r/r-l & b+t/t-b) is actually doing in the projection matrix? The only thing I got till now is headache :) Can you please help?

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