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| calculating the frustum |
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cherryyosh Member since: 12/5/2008 |
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 Posted - 3/2/2009 3:13:02 PM |
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| hey guys, I have started to create a visual debugger for my lighting system but am currently stuck on how to calculate the light's view frustum. anyone have any ideas or links?? (my google'ing skills fail me ) |
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zedz Member since: 2/15/2007 |
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 Posted - 3/2/2009 4:52:07 PM |
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| do a box from (-1,-1,-1)->(1,1,1) with the inverse of the lights projectionmodelview matrix ( I think thats correct ) |
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cherryyosh Member since: 12/5/2008 |
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Posted - 3/2/2009 5:25:28 PM |
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Quote: I think I might be getting the wrong inverse of the pmv.. Right now after rendering the shadowmap from the light I get the light's modelview then I mul the light's projection and store that as the pmv. glTranslatef( l->center[0], l->center[1], l->center[2] ); glGetFloatv( GL_MODELVIEW_MATRIX, modelView_shadow ); DrawScene(); glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, 0 ); glDisable( GL_POLYGON_OFFSET_FILL ); glPopAttrib(); glPopMatrix(); glMatrixMode( GL_PROJECTION ); //here we get the matrix needed later to draw the shadows correctly glMultMatrixf( modelView_shadow ); glGetFloatv( GL_PROJECTION_MATRIX, l->shadow_pmv ); from there I inverse that and load it into the current matrix before drawing a unti cube. this does not work.. |
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cherryyosh Member since: 12/5/2008 |
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Posted - 3/2/2009 8:05:23 PM |
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| can anyone help me get the correct inverse?? EDIT: I think I got it right, using the inverse modelView matrix, however this does not draw the correct frustum using a unit cube. Any ideas? [Edited by - cherryyosh on March 2, 2009 8:05:52 PM] |
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cherryyosh Member since: 12/5/2008 |
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Posted - 3/3/2009 3:18:17 PM |
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| any help please?? so annoyed by this.. should be easy! -_- |
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zedz Member since: 2/15/2007 |
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Posted - 3/3/2009 6:36:32 PM |
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| I just had a look first mult current matrix by inverse_modelview_matrix(light) the multiply that by inverse_projection_matrix(light) draw a cube |
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cherryyosh Member since: 12/5/2008 |
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Posted - 3/3/2009 7:18:03 PM |
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Quote: Im doing that now, and its still moving with the camera, even tried glLoadIdentity() before... heres the full code where I get the matrices
//for( int i = 0; i < NUMLIGHTS; i++ ){
// if( !light[i].isEnabled )
// break; //no need to do anything
Light* l = light;
//set set and pop the matrixes so nothing is saved
//NOTE: NOT OGL3.0, needs to be changed, how I dont know
glMatrixMode( GL_PROJECTION );
glPushMatrix();
glMatrixMode( GL_MODELVIEW );
glPushMatrix();
//set the viewport so we only draw what the map can haddel
//dont belive this is OGL3.0 either
//also very similar to sissors test, speed test??
glPushAttrib( GL_VIEWPORT_BIT );
glViewport( 0, 0, l->width, l->height );
//prevent z-fighting
glPolygonOffset( 1.0, 4096.0 );
glEnable( GL_POLYGON_OFFSET_FILL );
glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, shadow1FBO );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glTranslatef( l->center[0], l->center[1], l->center[2] );
glGetFloatv( GL_MODELVIEW_MATRIX, tmp );
Inverse( mvInv, tmp );
DrawScene();
glBindFramebufferEXT( GL_FRAMEBUFFER_EXT, 0 );
glDisable( GL_POLYGON_OFFSET_FILL );
glPopAttrib();
glPopMatrix();
glMatrixMode( GL_PROJECTION );
glGetFloatv( GL_PROJECTION_MATRIX, tmp );
Inverse( projInv, tmp );
glPopMatrix();
glMatrixMode( GL_MODELVIEW );
and the code to draw the frustum
glPushMatrix();
glMultMatrixf( mvInv );
glMultMatrixf( projInv );
glColor3f( 1.0, 0.0, 0.0 );
DrawUnitCube();
glPopMatrix();
and, thought I am sure this is correct, here is how I inverse the matrix void Inverse(float dst[16], float src[16]){ dst[0] = src[0]; dst[1] = src[4]; dst[2] = src[8]; dst[3] = 0.0f; dst[4] = src[1]; dst[5] = src[5]; dst[6] = src[9]; dst[7] = 0.0f; dst[8] = src[2]; dst[9] = src[6]; dst[10] = src[10]; dst[11] = 0.0f; dst[12] = -(src[12] * src[0]) - (src[13] * src[1]) - (src[14] * src[2]); dst[13] = -(src[12] * src[4]) - (src[13] * src[5]) - (src[14] * src[6]); dst[14] = -(src[12] * src[8]) - (src[13] * src[9]) - (src[14] * src[10]); dst[15] = 1.0f; } |
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zedz Member since: 2/15/2007 |
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Posted - 3/3/2009 8:39:09 PM |
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| thats not an inverse of a 4x4 matrix (that looks like a transpose, which is a lot easier, though it could be the inverse of a 3x3 matrix I think) anyways have a look at an existing math library for an example of the inverse, heres code in the matrix FAQ http://web.archive.org/web/20041029003853/http:/www.j3d.org/matrix_faq/matrfaq_latest.html#Q24 |
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cherryyosh Member since: 12/5/2008 |
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Posted - 3/3/2009 8:57:21 PM |
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Quote: Really, ill check it out.. Thats really odd that the inverse isnt right thought as I got the code from a nvidia demo.. thanks for the info ill report back when I get a working inverse. EDIT: desided it might be best if I use a preexisting libary for speed / full function.. But having a problem finding a good one. Anyone have any ideas on a good libary ( want cross platform, as if it wont be hah)? [Edited by - cherryyosh on March 3, 2009 9:57:13 PM] |
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cherryyosh Member since: 12/5/2008 |
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Posted - 3/4/2009 12:41:44 AM |
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Ok so I got a matrix class, the one nvidia supply. It seems like I copyed the cameraInverse function that I guess was simply a transpose, believe I read somewhere that for camera functions that works.. but might be wrong.. Anyways the unit cube is now always draw behind the camera, and can only been seen when moving the camera backwards. Just incase this is doing the wrong inverse I will post the code. (NOTE: T is float )
friend matrix4 inverse( const matrix4 & m) {
matrix4 minv;
T r1[8], r2[8], r3[8], r4[8];
T *s[4], *tmprow;
s[0] = &r1[0];
s[1] = &r2[0];
s[2] = &r3[0];
s[3] = &r4[0];
register int i,j,p,jj;
for(i=0;i<4;i++) {
for(j=0;j<4;j++) {
s[i][j] = m.element(i,j);
if(i==j) s[i][j+4] = 1.0;
else s[i][j+4] = 0.0;
}
}
T scp[4];
for(i=0;i<4;i++) {
scp[i] = T(fabs(s[i][0]));
for(j=1;j<4;j++)
if(T(fabs(s[i][j])) > scp[i]) scp[i] = T(fabs(s[i][j]));
if(scp[i] == 0.0) return minv; // singular matrix!
}
int pivot_to;
T scp_max;
for(i=0;i<4;i++) {
// select pivot row
pivot_to = i;
scp_max = T(fabs(s[i][i]/scp[i]));
// find out which row should be on top
for(p=i+1;p<4;p++)
if (T(fabs(s[p][i]/scp[p])) > scp_max) {
scp_max = T(fabs(s[p][i]/scp[p]));
pivot_to = p;
}
// Pivot if necessary
if(pivot_to != i) {
tmprow = s[i];
s[i] = s[pivot_to];
s[pivot_to] = tmprow;
T tmpscp;
tmpscp = scp[i];
scp[i] = scp[pivot_to];
scp[pivot_to] = tmpscp;
}
T mji;
// perform gaussian elimination
for(j=i+1;j<4;j++) {
mji = s[j][i]/s[i][i];
s[j][i] = 0.0;
for(jj=i+1;jj<8;jj++)
s[j][jj] -= mji*s[i][jj];
}
}
if(s[3][3] == 0.0) return minv; // singular matrix!
//
// Now we have an upper triangular matrix.
//
// x x x x | y y y y
// 0 x x x | y y y y
// 0 0 x x | y y y y
// 0 0 0 x | y y y y
//
// we'll back substitute to get the inverse
//
// 1 0 0 0 | z z z z
// 0 1 0 0 | z z z z
// 0 0 1 0 | z z z z
// 0 0 0 1 | z z z z
//
T mij;
for(i=3;i>0;i--) {
for(j=i-1;j > -1; j--) {
mij = s[j][i]/s[i][i];
for(jj=j+1;jj<8;jj++)
s[j][jj] -= mij*s[i][jj];
}
}
for(i=0;i<4;i++)
for(j=0;j<4;j++)
minv(i,j) = s[i][j+4] / s[i][i];
return minv;
}
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