Hey there.... I am looking for tutorials on frustum culling. I have read Mark Morley''s tutorial and it has everything except an explanation of the calculations he uses. The technique he outlines works but I need to know how the calculations were derived. If anyone can point me to more info or just explain it, that would be great. Implementation without theory only create blind spots. For those that care... this is the code that extracts the view frustum: ExtractFrustum() { float proj[16]; float modl[16]; float clip[16]; float t; /* Get the current PROJECTION matrix from OpenGL */ glGetFloatv( GL_PROJECTION_MATRIX, proj ); /* Get the current MODELVIEW matrix from OpenGL */ glGetFloatv( GL_MODELVIEW_MATRIX, modl ); /* Combine the two matrices (multiply projection by modelview) */ clip[ 0] = modl[ 0] * proj[ 0] + modl[ 1] * proj[ 4] + modl[ 2] * proj[ 8] + modl[ 3] * proj[12]; clip[ 1] = modl[ 0] * proj[ 1] + modl[ 1] * proj[ 5] + modl[ 2] * proj[ 9] + modl[ 3] * proj[13]; clip[ 2] = modl[ 0] * proj[ 2] + modl[ 1] * proj[ 6] + modl[ 2] * proj[10] + modl[ 3] * proj[14]; clip[ 3] = modl[ 0] * proj[ 3] + modl[ 1] * proj[ 7] + modl[ 2] * proj[11] + modl[ 3] * proj[15]; clip[ 4] = modl[ 4] * proj[ 0] + modl[ 5] * proj[ 4] + modl[ 6] * proj[ 8] + modl[ 7] * proj[12]; clip[ 5] = modl[ 4] * proj[ 1] + modl[ 5] * proj[ 5] + modl[ 6] * proj[ 9] + modl[ 7] * proj[13]; clip[ 6] = modl[ 4] * proj[ 2] + modl[ 5] * proj[ 6] + modl[ 6] * proj[10] + modl[ 7] * proj[14]; clip[ 7] = modl[ 4] * proj[ 3] + modl[ 5] * proj[ 7] + modl[ 6] * proj[11] + modl[ 7] * proj[15]; clip[ 8] = modl[ 8] * proj[ 0] + modl[ 9] * proj[ 4] + modl[10] * proj[ 8] + modl[11] * proj[12]; clip[ 9] = modl[ 8] * proj[ 1] + modl[ 9] * proj[ 5] + modl[10] * proj[ 9] + modl[11] * proj[13]; clip[10] = modl[ 8] * proj[ 2] + modl[ 9] * proj[ 6] + modl[10] * proj[10] + modl[11] * proj[14]; clip[11] = modl[ 8] * proj[ 3] + modl[ 9] * proj[ 7] + modl[10] * proj[11] + modl[11] * proj[15]; clip[12] = modl[12] * proj[ 0] + modl[13] * proj[ 4] + modl[14] * proj[ 8] + modl[15] * proj[12]; clip[13] = modl[12] * proj[ 1] + modl[13] * proj[ 5] + modl[14] * proj[ 9] + modl[15] * proj[13]; clip[14] = modl[12] * proj[ 2] + modl[13] * proj[ 6] + modl[14] * proj[10] + modl[15] * proj[14]; clip[15] = modl[12] * proj[ 3] + modl[13] * proj[ 7] + modl[14] * proj[11] + modl[15] * proj[15]; /* Extract the numbers for the RIGHT plane */ frustum[0][0] = clip[ 3] - clip[ 0]; frustum[0][1] = clip[ 7] - clip[ 4]; frustum[0][2] = clip[11] - clip[ 8]; frustum[0][3] = clip[15] - clip[12]; /* Normalize the result */ t = sqrt( frustum[0][0] * frustum[0][0] + frustum[0][1] * frustum[0][1] + frustum[0][2] * frustum[0][2] ); frustum[0][0] /= t; frustum[0][1] /= t; frustum[0][2] /= t; frustum[0][3] /= t; /* Extract the numbers for the LEFT plane */ frustum[1][0] = clip[ 3] + clip[ 0]; frustum[1][1] = clip[ 7] + clip[ 4]; frustum[1][2] = clip[11] + clip[ 8]; frustum[1][3] = clip[15] + clip[12]; /* Normalize the result */ t = sqrt( frustum[1][0] * frustum[1][0] + frustum[1][1] * frustum[1][1] + frustum[1][2] * frustum[1][2] ); frustum[1][0] /= t; frustum[1][1] /= t; frustum[1][2] /= t; frustum[1][3] /= t; /* Extract the BOTTOM plane */ frustum[2][0] = clip[ 3] + clip[ 1]; frustum[2][1] = clip[ 7] + clip[ 5]; frustum[2][2] = clip[11] + clip[ 9]; frustum[2][3] = clip[15] + clip[13]; /* Normalize the result */ t = sqrt( frustum[2][0] * frustum[2][0] + frustum[2][1] * frustum[2][1] + frustum[2][2] * frustum[2][2] ); frustum[2][0] /= t; frustum[2][1] /= t; frustum[2][2] /= t; frustum[2][3] /= t; /* Extract the TOP plane */ frustum[3][0] = clip[ 3] - clip[ 1]; frustum[3][1] = clip[ 7] - clip[ 5]; frustum[3][2] = clip[11] - clip[ 9]; frustum[3][3] = clip[15] - clip[13]; /* Normalize the result */ t = sqrt( frustum[3][0] * frustum[3][0] + frustum[3][1] * frustum[3][1] + frustum[3][2] * frustum[3][2] ); frustum[3][0] /= t; frustum[3][1] /= t; frustum[3][2] /= t; frustum[3][3] /= t; /* Extract the FAR plane */ frustum[4][0] = clip[ 3] - clip[ 2]; frustum[4][1] = clip[ 7] - clip[ 6]; frustum[4][2] = clip[11] - clip[10]; frustum[4][3] = clip[15] - clip[14]; /* Normalize the result */ t = sqrt( frustum[4][0] * frustum[4][0] + frustum[4][1] * frustum[4][1] + frustum[4][2] * frustum[4][2] ); frustum[4][0] /= t; frustum[4][1] /= t; frustum[4][2] /= t; frustum[4][3] /= t; /* Extract the NEAR plane */ frustum[5][0] = clip[ 3] + clip[ 2]; frustum[5][1] = clip[ 7] + clip[ 6]; frustum[5][2] = clip[11] + clip[10]; frustum[5][3] = clip[15] + clip[14]; /* Normalize the result */ t = sqrt( frustum[5][0] * frustum[5][0] + frustum[5][1] * frustum[5][1] + frustum[5][2] * frustum[5][2] ); frustum[5][0] /= t; frustum[5][1] /= t; frustum[5][2] /= t; frustum[5][3] /= t; } -The Headstones are talking... Can you hear them?

this exact question has been asked about a month ago on this forum. Use a search feature fo find it. (there is a link to thread on some other forum where someone explains this realy nice)

You are the best.... I have found the post and the link to the explanation by the most knowledgeable DigiBen. Thank you for your time.

If anyone cares, the post that was referred to is located at:
http://www.gametutorials.com/forum/topic.asp?TOPIC_ID=1708&FORUM_ID=4&CAT_ID=1&Topic_Title=help+on+frustum+culling&Forum_Title=Newbie

-The Headstones are talking... Can you hear them?

www.markmorley.com

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Leyder Dylan
http://ibelgique.ifrance.com/Slug-Production/