An array of numbers, symbols or expressions, arranged in row and columns. The numbers, symbols or expressions themselves are called elements or entries.
43
votes
8answers
5k 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
...
11
votes
5answers
545 views
Is there a common word that encompasses handling of position, rotation, and scale together?
I'm looking for a name for my class that manipulates 4x4 matrices that handle position, rotation, and scale. Is there a common word that encompasses all three?
(I'm splitting the matrix math into its ...
11
votes
6answers
3k views
Math topics for 3D graphics programming
I understand that the following math topics are required for 3D graphics programming. I have started doing some of them in my math course. Can someone point me in the direction of a resource that ...
10
votes
1answer
8k views
What is the correct order to multiply scale, rotation and translation matrices for a proper world matrix?
Assume DirectX as the platform, if that is important. (Pretty sure it isn't)
Assuming I have a proper scale, rotation and translation matrix, in what order do I multiply them to result in a proper ...
9
votes
2answers
2k views
How can I rotate about an arbitrary point in 3D (instead of the origin)?
I have some models that I want to rotate using quaternions in the normal manner, except instead of rotation about the origin, I want it to be offset slightly. I know that you don't say, in 3d space, ...
8
votes
4answers
1k views
Staggered Isometric Map: Calculate map coordinates for point on screen
I know there are already a lot of resources about this, but I haven't found one that matches my coordinate system and I'm having massive trouble adjusting any of those solutions to my needs.
What I ...
8
votes
1answer
380 views
Downprojecting an imaginary 4D mesh to the screen
As a mental exercise, I'm trying to imagine projecting an arbitrary 4D mesh onto the screen (2D).
I'm guessing a single 4D triangle would still consist of only 3 points, however each of those 3 ...
8
votes
1answer
1k views
Screen space to world space
I am writing a 2D game where my game world has x axis running left to right, y axis running top to bottom, and z axis out of the screen:
Whilst my game world is top-down, the game is rendered on a ...
8
votes
1answer
798 views
2D Skeletal Animation Transformations
I have been trying to build a 2D skeletal animation system for a while, and I believe that I'm fairly close to finishing. Currently, I have the following data structures:
struct Bone {
Bone ...
7
votes
1answer
2k views
Transform Matrix multiplication order
I am experiencing difficulties trying to figure out the correct multiplication order for a final transform matrix. I always get either strange movement or distorted geometry. My current model is ...
7
votes
3answers
993 views
Should I use a world matrix?
Image reference for the question:
(image from the CG tutorial)
The D3D9 API got us used to world matrices.
However, if you use world matrices, then you have to do an extra matrix multiply in the ...
7
votes
3answers
976 views
How do I adjust the origin of rotation for a group of sprites?
I am currently grouping sprites together, then applying a rotation transformation on draw:
private void UpdateMatrix(ref Vector2 origin, float radians)
{
Vector3 matrixorigin = new ...
7
votes
2answers
403 views
Portal Projection
Ok ok I admit, I'm bored and toying with a portal script like the one on steam.
I've figured out the following:
relative positioning of the mirrored cameras
render to texture for the portal (the ...
6
votes
5answers
903 views
Can someone explain the (reasons for the) implications of colum vs row major in multiplication/concatenation?
I am trying to learn how to construct view and projection matrices, and keep reaching difficulties in my implementation owing to my confusion about the two standards for matrices.
I know how to ...
6
votes
1answer
187 views
Matrices: Arrays or separate member variables?
I'm teaching myself 3D maths and in the process building my own rudimentary engine (of sorts). I was wondering what would be the best way to structure my matrix class. There are a few options:
...
6
votes
4answers
349 views
How can I generate a view or projection matrix for OpenGL 3.+
I'm transitioning from OpenGL 2 to OpenGL 3.+ and to GLSL 1.5. I'm trying to avoid using the deprecated features.
My question how do we now generate the view or projection matrix. I was using the ...
6
votes
3answers
1k views
Direct3D and OpenGL Matrix representation
As I read in OpenGL matrices are column major. It means that if I create a 16 element array first four elements are the first column in matrix. Is it the same for Direct3D or any transformation's ...
6
votes
1answer
4k views
Help understanding gluLookAt()
I am fairly new to openGL( 3 months ) and am asking for assistance in understanding the fundamentals behind gluLookAt().
Currently I have spent most of my time with openGL modeling scenes with fixed ...
6
votes
2answers
316 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 ...
6
votes
2answers
819 views
Vector games (Wireframe, Elite-like) theory and implementations?
I'm interesting in knowing more about how vector games like Elite and Star Wars Atari were built from grounds up. The question is not how to implement vector graphics with modern 3D APIs like OpenGL ...
6
votes
2answers
686 views
What is eigenvalue decomposition and why would it be useful in games?
In various math libraries developed for game engines, I see 2x2 and 3x3 square matrices having this function (along with some helper functions). I tried to find information regarding it but did not ...
6
votes
1answer
240 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 ...
5
votes
3answers
647 views
What's a pre-multiplied 4x4 matrix?
I'm using a 3d game engine, that uses a 4x4 matrix to modify the camera projection.
The matrix is in the regular 4x4 format:
r r r x
r r r y
r r r z
- - - zoom
The description for the ...
5
votes
3answers
660 views
Why is my model's scale changing after rotating it?
I have just started a simple flight simulator and have implemented Roll and pitch. In the beginning, testing went very well; however, after about 15-20 seconds of constantly moving the thumbsticks in ...
5
votes
1answer
785 views
Problem with Assimp 3D model loader
In my game I have model loading functions for Assimp model loading library. I can load the model and render it, but the model displays incorrectly. The models load in as if they were using a seperate ...
5
votes
3answers
1k views
XNA 4.0: 2D Camera Y and X are going in wrong direction
I asked this question on stackoverflow but assumed this might be a better area to ask it as well for a more informed answer.
My problem is that I am trying to create a camera class and have it so ...
5
votes
1answer
237 views
Realistic damage
I'm looking for a good way to simulate damage, for example a weapon firing at a ship it would calculate the damage depending on layer type, weapon type, angle and similar what i need is a way to to ...
5
votes
1answer
342 views
How do I create weapon attachments?
My question is; I am developing a game for XNA and I am trying to create a weapon attachment for my player model. My player model loads the .md3 format and reads tags for attachment points. I am able ...
5
votes
1answer
92 views
Rotating plane to be parallel to given normal via change of basis
I have two planes and their respective normals. I would like to rotate the second plane, planeB, so that it is parallel to the first, planeA.
To do this, I am using a change of basis to rotate each ...
5
votes
2answers
212 views
Randomly generated track
I would like to create randomly generated track from one point to another with specified length of that track (it can be 2 more or less as a result of that function) in matrix. I have function called ...
5
votes
3answers
615 views
Arbitrary projection matrix from 6 arbitrary frustum planes
A projection matrix represent a tranformation from the camera view space to the rendering system clip space. In other words, it defines the transormation between a 6-sided frustum to the clip cube.
...
4
votes
3answers
2k views
Inverting matrix in HLSL
I've got an object in HLSL and I'm using hardware instancing to render multiple copies. But I've come a bit of a cropper when it comes to the vertex normals. Currently I am not using normal mapping ...
4
votes
2answers
624 views
Ara matrices calculated on the GPU or on the CPU? Would built-in matrix functions be faster than my custom ones?
If I add a math library (for example containing a Matrix class) and use it in my program drawing with OpenGL, will my be work slower than if I used standard OpenGL functions for matrix calculations? ...
4
votes
1answer
498 views
Multiplication for MVP matrices: Any benefits to doing so within the vertex shader?
I'd like to understand under what circumstances (if any) it is worth doing MVP matrix multiplication inside a vertex shader.
The vertex shader is run once per vertex, and a single mesh typically ...
4
votes
2answers
811 views
Should the modelview and projection matrices be calculated in the shader or on the CPU?
At minimum I would have a camera with rotation and world position; projections parameters such as angle of view and perspective vs. orthographic; and meshes with scale, angle, and world position.
...
4
votes
1answer
321 views
UVW: better explanation, and how to implement with GLES texture2D()
UVW texture coordinates, as opposed to UV texture coordinates, do not get very adequate explanation on the web. Many people offer the simple exlanation, "UV is for 2-dimensional textures and UVW are ...
4
votes
2answers
845 views
Matrix for 2D perspective
I'm trying to determine whether what I'm attempting to achieve is even possible mathematically. I'm obviously not a seasoned game developer so I'm having trouble even coming up with the terminology to ...
4
votes
1answer
270 views
Getting the Bounds of a 2D Cameras View with Zoom
I am using a 2D camera, which does rotations and zoom. Currently, I am using the following to get my MinX, MinY, MaxX and MaxY...
public float MinX
{
get
{
return ...
4
votes
1answer
437 views
Managing Game Entity coordinates
In my Game I'm currently have "Scene Coordinates" which are the X,Y coordinates relative to a Game Scene.
In that Scene there are Game Entities, let's say there's a GameEntity A in x=100.0, y=100.0 ( ...
4
votes
1answer
117 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 ...
4
votes
1answer
215 views
Projecting onto different size screens by cropping
I am building a phone application which will display a shape on screen. The shape should look the same on different screen sizes. I Decided the best way to do this is to show more of the background on ...
4
votes
3answers
520 views
Mapping 3D object coordinates to 2D screen coordinates with perspective projection
Sort of following on from where this person was in their topic:
Matrix for 2D perspective
What I have at the moment is a transformation matrix that's defined as follows:
http://pastebin.com/GM6BhP0R
...
4
votes
1answer
222 views
Translation from one coordinate system to another having Z-offset issues
I'm using ARToolkit to do an augmented reality application, but my problem is really with the 3D coordinates.
In this application, I use my webcam to generate the scene. I have two markers (printed ...
4
votes
4answers
919 views
From camera coordinates to world coordinates
I want to calculate world coordinates from camera coordinates. However, I seem to have problems with my understandings of how matrices in HLSL work.
From world to camera is clear:
cameraPosition = ...
4
votes
1answer
555 views
Problem with DirectX scene-graph
I'm trying to implement a basic scene graph in DirectX using C++. I am using a left child-right sibling binary tree to do this.
I'm having trouble updating each node's world transformation relative to ...
4
votes
1answer
279 views
apply non-hierarchial transforms to hierarchial skeleton?
I use Blender3D, but the answer might not API-exclusive.
I have some matrices I need to assign to PoseBones. The resulting pose looks fine when there is no bone hierarchy (parenting) and messed up ...
3
votes
1answer
1k views
Can a 4x4 matrix describe a camera's perspective?
I'm working with a closed-source 3D engine, and it only allows you to set the view projection via a 4x4 matrix. Can this matrix describe the camera's translation, rotation & perspective?
I turned ...
3
votes
2answers
479 views
When constructing an orientation matrix, are the rows of the matrix the axis?
When constructing an orientation matrix, are the rows of the matrix the axis?
The matrix is row-major and I'm multiplying vectors on the right (Mv). So, the matrix looks like
r0c0 r0c1 r0c2
r1c0 ...
3
votes
3answers
231 views
Tetris - Rotations using Linear Algebra (Rotation Matrices)
I'm making Tetris in Java and am at the point of rotations... Originally I was hardcoding each rotation:
if (direction.equals("right")) {
if (shape.equals("Bar")) {
if ...
3
votes
3answers
714 views
How to calculate the inverse of a 4*4 opengl transform matrix
I am transforming my camera like any other object. I would like to set the view model matrix to the inverse of this so that I can draw the rest of the objects relative to the camera.
How do i ...
