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.

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44 views

Rotation matrix is being inconsistent with pitch and roll

I'm calculating the rotation matrix for a turret when it's at an angle in Javascript. I have XYZ co-ords for the turret and target with X being 90 degrees right, Y being straight ahead and Z being ...
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1answer
54 views

opengl matrix multiplication

Can someone provide some type of example of multiplying a 4x4 matrix without using loops? typedef struct matrix4 { data[16]; } m4; can someone provide a sample of how you you'd multiply two of ...
4
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1answer
139 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 ...
2
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1answer
82 views

How to calculate if a point is contained in rectangular camera viewport with rotation?

I am working with my camera, and am trying to improve it so that I can calculate if a world point is on screen, taking rotation into account. Currently, my camera rectangle is calculated as so: ...
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0answers
35 views

When use LookAt or Inverted world matrix to compute View Matrix?

I am reading this article http://www.3dgep.com/understanding-the-view-matrix/ and it says that View Matrix is the inverted matrix of World (or Model) Matrix but in the first approach the article ...
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1answer
208 views

reflection plane 3d

Hey there I'm trying to create a plane that can have a texture on it and reflect the 3d elements around it. for example a plane with a laminate floor texture and above it a cube rotating. I want the ...
9
votes
2answers
896 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. ...
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vote
1answer
254 views

Camera lookAt target changes when rotating parent node

have the following issue.I have a camera with lookAt method which works fine.I have a parent node to which I parent the camera.If I rotate the parent node while keeping the camera lookAt the target , ...
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1answer
64 views

How to understand kind of matrix/world from implemented math operations?

i'm a newbie in 3d programming, and i approach for the first time this argument. I try to make some changes to an existing 3d object viewer, to better suite my needs. This object viewer is jsc3d. I ...
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1answer
49 views

16-byte aligned matrix in DirectX9 and D3DX with Havok Physics 2012

I want to ask a question about D3DXMATRIX and D3DXMATRIXA16, and how to use them with Havok Physics. I'm using Visual Studio 2012 on Windows 8. I successfully created an instance of hkpWorld, added ...
2
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2answers
2k 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. ...
7
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1answer
104 views

How can I keep the clicked point under the mouse when rotating? (GLM)

I have a spherical mesh of radius 1, centered at (0,0,0) in world coordinates. I want to rotate the sphere so that the clicked point remains under the mouse at all times. However, I cannot find an ...
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2answers
99 views

Problems with Rotation Matrices on Certain Axes

Here is what my rotation matrix looks like: public Matrix4f initRotation(float x, float y, float z) { Matrix4f rx = new Matrix4f(); Matrix4f ry = new Matrix4f(); Matrix4f rz = new ...
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vote
1answer
44 views

Rotate an objects velocity

I have a collision system (in 3D but for the purpose of the question assume 2D) where I want to calculate the new velocity (stored as a vector) after a collision. What I have is the velocity of the ...
28
votes
5answers
6k views

Why do we use 4x4 matrices to transform things in 3D?

To translate a vector by 10 unit in the X direction, why do we have to use a matrix? We can just add 10 to the mat[0][0], and we got the same result too.
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0answers
109 views

Adding a 2D transformation matrix to GLSL

I'm having trouble understanding the matrices I need to render an object in OpenGL. I've been using a matrix to make up for the translation and scaling from the camera in my game but I didn't have a ...
2
votes
1answer
794 views

multiply matrix by vector: what to do if need to change y-up to z-up?

I multiply a matrix with a position vector to get a new position, however, now I need to change my matrix from y-up coordinate space to z-up. Changing only the matrix won't work: how to apply the ...
3
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1answer
185 views

How to make an object stay relative to another object

In the following example there is a guy and a boat. They have both a position, orientation and velocity. The guy is standing on the shore and would like to board. He changes his position so he is ...
3
votes
1answer
381 views

Retrieving model position after applying modeltransforms in XNA

For this method that the goingBeyond XNA tutorial provides, it would be really convenient if I could retrieve the new position of the model after I apply all the transforms to the mesh. I have edited ...
0
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1answer
187 views

Relative Position/Rotation calculation

I have 2 objects each with a 3x3 Matrix (Orientation) and a Vector3 (Translation). Both are relative to world coordinates. How do I calculate the position and orientation of object B in relation to ...
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vote
3answers
347 views

2D HLSL World position

I'm trying to get world position from my vertex shader to my pixel shader so that I can disable the shader once a preset X coordinate has been passed (no shading once I'm over X). Getting the screen ...
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0answers
36 views

Coordinates estimation

Hi im using artoolkit to extract the coordinates of the marker im detecting with the camera. I need to know the values returned when arGetTransMat is the coordinates (x,y,z) which is returned ...
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1answer
136 views

Pre-calculating skeletal animation data

I'm working on skeletal animation and so far I've got the skeleton drawn with interpolated animation working (just on the cpu still). I was thinking about changing my file format for my skeleton and ...
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0answers
67 views

OpenGL - Cubemap “Rotating” Proportional To Camera Movement

I'm doing a simple planet rendering project and am running into an issue with accessing cubemap textures correctly. The planet terrain is generated using the diamond square algorithm done 6 times and ...
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3answers
62 views

Problems Animating Texture in OpenGL

I'm trying to animate a texture to scroll a static screen for a television, however I'm having some issues. Just translating within the texture matrix animates all textures in the scene which is ...
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2answers
151 views

How can I calculate the orthographic projection needed to encompass an object with arbitrary rotation?

So I need to set up the dimensions of a orthographic projection that will encompass the entirety of a bounding box when viewed from any arbitrary position. That's an eye (programmer art); and the ...
0
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1answer
112 views

how to stop camera at the end of world map when zoomed in

Im building a tile-based game, and Im trying to implement zooming in on the center of the screen. My problem is, when I get to the edge of the map and im zoomed in, Im noticing that my camera doesn't ...
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2answers
122 views

OpenGL: Is it efficient ok to glPushMatrix, plMultMatrix, plPopMatrix for every object in my scene?

I'm very new to opengl, and I might not fully understand the openGL matrix projection stack thing. So, I have about 300 'objects' in my scene, each with their own position/rotation, and I want to ...
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0answers
148 views

Confused About My Code Suggesting The Normal Matrix Is Equivalent To The ModelView Matrix

I'm learning environment mapping in OpenGL by following this page. In his vertex shader, the author calculates the vertex normal in eye space with the following code: nEye = vec3(viewMatrix * ...
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0answers
40 views

2D viewport matrix World to Local coordinates

I would like to use a Matrix but it causes (or I think it does) problems with accuracy. Clearly classic float matrix causes jaggy movement/accuracy issues. The reason is that my objects have real ...
12
votes
3answers
1k views

Rotate object around fixed axis

I am trying to let the user of my app rotate a 3D object drawn in the center of the screen by dragging their finger on screen. A horizontal movement on screen means rotation around a fixed Y axis, and ...
0
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0answers
88 views

Coordinate system in OGLdev tutorials

Working with OGLdev tutorials http://ogldev.atspace.co.uk/ I found that this code uses coordinate system, which doesn't look like in most other samples. Positive x-axis direction is left, and not ...
0
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1answer
41 views

Matrix Rotation Only Works On one Axis At A Time

I have this function in my vertex shader. It makes a transformation matix out of a transformation matrix, a rotation and an intensity. It works just fine when setting the rotation of one of the axis ...
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0answers
124 views

Pre- or post-multiplication for rotation between coordinate frames

I have three 3D coordinate frames: O, A and B, as shown below. I want to know the rotation matrix RAB between A and B, that is the rotation that is required, with respect to the frame A, to move ...
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1answer
57 views

Inline-Building a World (SRT) Matrix

Currently, to construct a world matrix, I have the following code: return FromScale(scale) * rotation.RotMatrix * FromTranslation(translation); However, this is constructing three matrices, and ...
69
votes
9answers
30k 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 ...
5
votes
3answers
461 views

Why do we refer to a “model view” matrix and not a “viewprojection” matrix?

Why there is a model-view matrix, but not a view-projection matrix? A view-projection matrix would make much more sense to me, since every entity in the scene has his own position and therefore its ...
2
votes
1answer
233 views

Project rotated matrix to isometric coordinate

I have a group of soldiers, and each has a vector describing their position in the squad. When the group rotates, I do this math to calculate the desired position of each soldier. var unitPositions : ...
0
votes
1answer
247 views

how to retain the animated position in opengl es 2.0

I am doing frame based animation for 300 frames in opengl es 2.0 I want a rectangle to translate by +200 pixels in X axis and also scaled up by double (2 units) in the first 100 frames Then, the ...
0
votes
0answers
54 views

Use Android 4x5 ColorMatrix in OpenGL ES 2 Shader

I am trying to use Android Color Matrix in OpenGL ES 2. I have been able to use a 4x4 Matrix using the following code in the Shader (this adds also an intensity parameter): varying vec2 ...
0
votes
0answers
60 views

GLSL billboarding

I want to make billboarding using GLSL. For what I've got so far it works, but not exactly the way I want. My vertex shader looks like this: #version 120 uniform float partSize; varying vec2 ...
0
votes
1answer
97 views

Scaling world - projection, view or separate matrix?

I am currently writing a simple 3D space visualisation program. Things get loaded into it from a simple XML file, which contains positions and sizes of objects in space, so you can put basically any ...
0
votes
1answer
120 views

Binding an Instance Matrix with an InputLayout

If I want to bind an instance matrix to a vertex shader, how do I go about it? For example, here is a super-simple VS input: struct VS_IN { float4 Position : POSITION; row_major float4x4 ...
1
vote
1answer
126 views

How to position a Weapons model in a first person shooter with XNA

I am building a first person shooter and positioning the weapons is hard. I am trying to get the bat to look like you are holding it but I keep trying things and they don't appear in the positions I ...
4
votes
1answer
65 views

How can I find the minimal texture size so the texture requires no pixel interpolation when transformed by a given matrix?

Given a rectangle with width x and height y, and a transformation matrix T: How can I estimate the minimal resolution of the texture (that is, its width and height) such the interpolation of ...
3
votes
1answer
141 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 ...
1
vote
1answer
158 views

Get 3D quad rotation matrix from points

I have 4 3D points which represent a even quad in space. (So 3 points are sufficient) I need to get all the individual transformations (translation, rotation, dimensions) so that I can build that quad ...
3
votes
1answer
143 views

What is FOVx in this diagram?

a beginner game developer here. I have recently taken upon learning about 3D game development and I am stuck on a simple matrix problem. The image is found from this article: ...
2
votes
1answer
1k views

OpenGL light appears to move with camera and changes with object rotation

I have a working open gl es 2.0 3d engine (my own) that I've used in several iOS apps. I recently noticed that on a mutli-symmetrical object the lighting didn't look the same at each rotation. For ...
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0answers
34 views

Connecting a model's joint to the joint of another model

I am trying to figure out the math behind orientating and translating a model so that a specified point on the model will connect with a specified point on another model. For example, given the ...