# Tagged Questions

A 2D array of numbers, symbols or expressions, arranged in rows and columns. Each row must have the same number of columns. The numbers, symbols or expressions themselves are called elements or entries.

835 views

### getting bone base and tip positions from a transform matrix?

I need this for a Blender3d script, but you don't really need to know Blender to answer this. I need to get bone head and tip positions from a transform matrix read from a file. The position of base ...
501 views

### How to move an object up and down like a wave?

I am trying to move my object up and down using cos and sin, but I have problem understanding how does the sin and cos work, so I can make my object move up and down like a wave frequently Init Time ...
1k views

### Orthographic Projection with variable FOV

We are building agame with orthographic view. The problem we face is the fact that with different resolution you can see different area of the game world. E.g. if you have higher resolution you can ...
696 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 ...
611 views

### HLSL What you get when you subtract world position from InvertViewProjection.Translation?

In one of NVIDIA's Vertex shaders (the metal one) I found the following code: // transform object normals, tangents, & binormals to world-space: float4x4 WorldITXf : WorldInverseTranspose < ...
1k views

### Need to translate a Rotation Matrix to Rotation y, x, z OpenGL & Jitter for 3D Game

I am using the Jitter Physics engine which gives a rotation matrix: M11 M12 M13 M21 M22 M23 M21 M32 M33 And I need it so OpenGL can use it for rotation GL.Rotate(xr, 1, 0, 0) GL.Rotate(yr, 0, 1, 0)...
1k views

### Camera for 2.5D Game

I'm hoping someone can explain this to me like I'm 5, because I've been struggling with this for hours and simply cannot understand what I'm doing wrong. I've written a Camera class for my 2.5D game. ...
169 views

### Unproject considering parallax depth

How can I take screen coordinates (or alternatively world coordinates on the 'primary' parallax plane) and find out what world coordinates they translate into when taking parallax depth into account? ...
1k views

### View Matrix from Camera in Unity Script

I am looking to get a Camera component's "view" matrix in a script. I see that I can get the projection matrix using Camera.projectionMatrix, but I don't see a Camera.viewMatrix property... I want ...
842 views

### switching from third person view to first person view

I have done a scene in opengl where I'm using a third person camera (that I can control with the mouse). Then, inside it, it has the camera of the first view (that I called thirdpersonCamera, see the ...
5k views

### Combining rotation,scaling around a pivot with translation into a matrix

In short: I need to combine rotation (in the form of a quaternion), scaling around a pivot point along with translation into a transformation matrix. The long: I am trying to implement a proprietary ...
603 views

### How to properly translate a point by a matrix?

I wrote a simple Matrix class and it has methods like rotate, translate, etc. They all seem to be working, but whenever I try to translate a rectangle using the matrix, the translation axis seem to be ...
119 views

### Last Matrix operation ignored?

I have 2 methods, one to rotate my Quad and one to flip it (using scaleM), they are as follows: (Note, all values in these methods have been properly defined). If I call just one, they work as ...
134 views

### Rotate view matrix based on touch coordinates

I'm working on an Android game where I need to rotate the camera around the origin based on the user dragging their finger. My view matrix has initial position of sitting on the negative z and facing ...
217 views

### Implementing axonometric bird-view in XNA

I made all kinds of logic (waypath, aso) for my strategical game, based on XNA (monogame). Now I "misused" the Vector2 a little bit: As I'm working from a "top-down" perspective, I'm using the Y-axis ...
40 views

### Constrain parent node transform to child bounds

If I have some node rendering tree set up, where a node basically has a draw method to render things, and a transform, represented as a 3x3 matrix, with scale and translation. Now, I would like to ...
460 views

### Trying to convert as3 Matrix to C++ glm matrix

I am trying to convert a library called DragonBones to C++ Opengl which allows you to use Flash based skeletal animation. I'm almost done but I am running into a problem. I am trying to transform the ...
217 views

### Storing tile grid in a matrix: row major vs column major

I'm using a generic matrix container to store the tile grid for my RTS game. This is where I am confused: a matrix is traditionally row major, i.e. matrix(0, 10) means 'at 0th row, 10th column.' A ...
337 views

### How can shears/reflections/enlargements be represented by 4x4 matrices? [closed]

I understand that 4x4 matrices can represent transformations on a 3d point (represented as x, y, z, w) Eg, a translation is [1 0 0 0] [0 1 0 0] [0 0 1 0] [x y z 1] where x, y and z are the amount ...
186 views

### Pinhole matrix problem

I made a program to represent a 3D world. I use the projection matrix we can find on wikipedia. For viewing a scene it's very nice but when I straff in the scene, everything behind the camera go on ...
210 views

### XNA matrix order problem

I want a matrix that scales first and then rotates. I tried the code below, but it didn't work. zRotation, yRotation and xRotation are rotations that shouldn't be affected by the origin. allrot should ...
613 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?
539 views

### Creating a 2D perspective in 3D game

I'm new to XNA and 3D game development in general. I'm creating a puzzle game kind of similar to tetris, built with blocks. I decided to build the game in 3D since I can do some cool animations and ...
535 views

### Matrix multiplication - Scene Graphs

I wrote a MatrixStack class in C# to use in a SceneGraph. So, to get the world matrix for an object I am suposed to use: WorldMatrix = ParentWorld * LocalTransform But, in fact, it only works as ...
228 views

### Common way to store model transformations

I ask myself what's the best way to store the transformations in a model class. What I came up with is to store the translation and scaling in a Vector3 and the rotation in a Matrix4. On each update (...
474 views

### Sharp DX Identity Matrix, Matrix.Forward vector pointing at negative Z

I'm trying to take a steady grip on Sharp DX. Already done some work like translating, scaling and rotating objects. Now i have to calculate the rotation matrix using only direction vector and ...
289 views

### Stage3D: Camera pans the whole screen

I am trying to create a 2D Stage3D game where you can move the camera around the level in an RTS style. I thought about using Orthographic Matrix3D functions for this but when I try to scroll the ...
285 views

### Matrix transforms in XNA

So in my most recent 2D game I draw objects like so. _spriteBatch.Draw(_sprite, Center(), null, Color.White, _rotation, new Vector2(_sprite.Width / 2, _sprite.Height / 2), _scale, SpriteEffects....
2k views

### What is the difference between a modelview-projection matrix and world-view-projection matrix?

So basically I wrote a shader a long time ago that uses all World and WVP matrices. Now I am working in an engine that will only give me access to ModelView, MVP, and model to world space matrices. ...
191 views

### Manual GLU.gluUnproject

Before I used GLU.gluUnproject to calculate my picking ray in my OpenGL game. Recently I switched to my own calculated matrices, and now I can forget the gluUnproject. How can I calculate the picking ...
267 views

### Optimising skeletal animation

I am implementing a skeleton system for my latest game. I am using my own linear algebra classes which already have some optimisations, such as separate transformPoint and transformVector functions ...
544 views

### D3DXMatrixDecompose gives different quaternion than D3DXQuaternionRotationMatrix

In trying to solve this problem, I tracked down the problem to the conversion of the rotation matrix to quaternion. In particular, consider the following matrix: -0.02099178 0.9997436 -0.008475631 0 ...
233 views

### OpenGL Calculate Matrices

Im trying to switch from the glTranslate etc to my own Matrices, but for some reason it does not work. Here are my 2 functions to create the view- and projection matrix: public Matrix4f getViewMatrix(...
10k views

### OpenGL - Understanding the relationship between Model, View and World Matrix

I am having a bit of trouble understanding how these matrixes work and how to set them up in relation to one another to get a proper system running. In my understanding the Model Matrix is the matrix ...
105 views

### What values to construct “Projection Matrix” from?

I am curious to what standard values I should use to create a camera's projection matrix, as well as if certain measurements need to be taken if I want to represent a very small world or a very big ...
138 views

### Getting Rotation Values From A Rotation Matrix

I'm trying to get rotation values along the x, y and z axis from a matrix that can include rotation, translation and scale data. Currently I have this function to return the y rotational value: float ...
826 views

### Rotating and Translating a Node in Horde3D with Matrices and Quaternions

I have been trying to learn how to use the Horde3D rendering engine for the past couple of days, and so far I have managed to learn a decent amount and integrate Bullet Physics with it as well. My ...
147 views

### XNA Camera Positioning All Wrong

I've been working in 3DSMax for years now and decided to give XNA 4.0 a try. I've got the majority of it working, however the camera is being a pain to me and I can't discern what's gone wrong. I ...
190 views

### What kind of projection is ScreenX=X/Z, ScreenY=Y/Z?

I have an existing class which transforms 3D vectors and projects them on a 2D plane (Camera). The code is all written in C without help from an external library. To project a single vector (X,Y,Z) ...
824 views

### Negative scale in Matrix 4x4

After some rotations and to from quaternion conversions I get negative scale from Matrix 4x4, is it possible? I need that scale to draw sprite on screen so I get sprite flipped, how to deal with this ...
438 views

### Java Tetris - Matrix Rotations

I'm building Tetris in Java and am trying to use linear algebra to rotate a piece composed of 4 tiles. My friend was explaining the way to do it is: He said: "To clarify, you do need to rotate ...
2k 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 (...
1k 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 ...
590 views

### Translating Viewmatrix is inverted, why?

So I've defined a Projectionmatrix, Viewmatrix and a Modelmatrix using OpenGL (LWJGL). But when I translate my Viewmatrix to +X it moves my object to the right (hence my camera is moving to the left),...
2k views

### Scaling along an arbitrary axis (Dealing with non-uniform scale)

I'm trying to build my own little engine to get more familiar with the concepts of 3D programming. I have a transform class that on each frame it creates a Scaling Matrix (S), a Rotation Matrix from ...
177 views

### Transform translation relative to world space

What is common algorithm for translating a transform matrix relative to world space axis? E.g. Matrix M is representing some local space. When I want to translate M relative to it's own local axis, I ...
655 views

### Xna Equivalent of Viewport.Unproject in a draw call as a matrix transformation

I am making a 2D sidescroller and I would like to draw my sprite to world space instead of client space so I do not have to lock it to the center of the screen and when the camera stops the sprite ...
218 views

### Camera not strafing (GLSL)

I use this code in my GLSL vertex shader, where v_position is the vertex position: gl_Position = v_position * u_camera; and set u_camera as follows: meshShader.setUniformMatrix("u_camera", camera....