# Difference between revisions of "GluLookAt code"

m (categorizing) |
Blue Prawn (talk | contribs) m (update old link) |
||

Line 2: | Line 2: | ||

It is traditional and can be found in a lot of tutorials and examples.<br> | It is traditional and can be found in a lot of tutorials and examples.<br> | ||

gluLookAt's source code is very simple and can be replaced easily.<br> | gluLookAt's source code is very simple and can be replaced easily.<br> | ||

− | The code here comes from glh library (OpenGL Helper Library) | + | The code here comes from glh library (OpenGL Helper Library), LGPL license |

+ | https://sourceforge.net/projects/glhlib<br> | ||

<br> | <br> | ||

<br> | <br> |

## Revision as of 01:16, 25 May 2010

GLU - the OpenGL Utility library is an additional library that contains a handful of functions for additional tasks.

It is traditional and can be found in a lot of tutorials and examples.

gluLookAt's source code is very simple and can be replaced easily.

The code here comes from glh library (OpenGL Helper Library), LGPL license
https://sourceforge.net/projects/glhlib

This function computes a matrix and multiplies it with whatever is in *matrix.

eyePosition3D is a XYZ position. This is where you are (your eye is).

center3D is the XYZ position where you want to look at.

upVector3D is a XYZ normalized vector. Quite often 0.0, 1.0, 0.0

The code presented here is slightly modified (but functional and correct) from the one in glhlib.

void glhLookAtf2(float *matrix, float *eyePosition3D, float *center3D, float *upVector3D) { float forward[3], side[3], up[3]; float matrix2[16], resultMatrix[16]; //------------------ forward[0] = center3D[0] - eyePosition3D[0]; forward[1] = center3D[1] - eyePosition3D[1]; forward[2] = center3D[2] - eyePosition3D[2]; NormalizeVector(forward); //------------------ //Side = forward x up ComputeNormalOfPlane(side, forward, upVector3D); NormalizeVector(side); //------------------ //Recompute up as: up = side x forward ComputeNormalOfPlane(up, side, forward); //------------------ matrix2[0] = side[0]; matrix2[4] = side[1]; matrix2[8] = side[2]; matrix2[12] = 0.0; //------------------ matrix2[1] = up[0]; matrix2[5] = up[1]; matrix2[9] = up[2]; matrix2[13] = 0.0; //------------------ matrix2[2] = -forward[0]; matrix2[6] = -forward[1]; matrix2[10] = -forward[2]; matrix2[14] = 0.0; //------------------ matrix2[3] = matrix2[7] = matrix2[11] = 0.0; matrix2[15] = 1.0; //------------------ MultiplyMatrices4by4OpenGL_FLOAT(resultMatrix, matrix, matrix2); glhTranslatef2(resultMatrix, -eyePosition3D[0], -eyePosition3D[1], -eyePosition3D[2]); //------------------ memcpy(matrix, resultMatrix, 16*sizeof(float)); }

The matrix you get can be uploaded with a call to glLoadMatrixf(matrix) or if you are using shaders, use glUniformMatrix4fv(location, 1, GL_FALSE, matrix).