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06.16.2008 at 04:58PM PDT, ID: 23489987

	[x] Attachment Details

Am I Doing this Matrix Multiplication Correctly?

Asked by Jamsb in 3D Game Programming

Tags: C++, OpenGL

Basically I have written a class to draw a cube centered on a point (XYZ). I perform various tranlations on my scene using glTranslate/glRotate. Now I want to calculate the new position of the cube ("world co-ordinates" if that is the right term.)

It has been suggested that I should multiple the Point by the Modelviewmatrix I have achieved this by doing the following (see code).

Is this code correct and will it do what I want it to?

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             //function to do multiplication
 
#include <gl/gl.h>
 
void MultiplyVMatrix(GLfloat* Vertex, GLfloat* Matrix, GLfloat* ResultMatrix)
{
	for(int i=0;i<16;i++)
		for(int j=0;j<4;j++)
		ResultMatrix[j]+=Matrix[i]*Vertex[j];
 
}        
 
**************************************************************
//modelview matrix and multiply co-ordinate of cube
 
GLfloat matrix[16];
GLfloat vertex[4]={1,2,-5,0}; //any co-ordinate for testing
GLfloat resultmatrix[4]={0,0,0,0};
 
glGetFloatv(GL_MODELVIEW_MATRIX, matrix); //grab the modelview matrix
 
MultiplyVMatrix(vertex,matrix,resultmatrix);

           
         

Attachments:

translation.gif (1 KB) (File Type Details)

My Cube :)

Keywords: Am I Doing this Matrix Multiplication Cor…

	Title
1	Multiplying by Modelview Matrix Gives …
2	parallel (Matrix-matrix multiplication)
3	Drawing an image into a scene
4	strassen's matrix multiplication algorithm
5	3D Projection of "real" XYZ coordin…
6	To draw cube, Pyramid in Delphi

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20080716-EE-VQP-32 / EE_QW_2_20070628

Am I Doing this Matrix Multiplication Correctly?

Asked by Jamsb in 3D Game Programming

Tags: C++, OpenGL

About this solution