SNEACKERS SNEACKERS Women SNEACKERS Women Guess Guess Women Guess Guess Guess SNEACKERS Women up vote 0 down vote favorite

Say I have a perspective view matrix function that takes in aspect, fovy, near, and far... Transforming the view into a frustum. Typical OpenGL stuff, right. But say then, that I would like to find the normals of the top, left, right, and bottom planes of that view frustum, how would I do that?

Edit: I forgot, the camera has a vector position, and a vector direction ...

up vote 1 down vote accepted

It becomes much clearer if you draw it from a top-down perspective:

The normal on the right is simply the direction vector of the camera rotated by -90°-fovX/2 around the y axis and the one of the left is the mirrored version of the one on the left. Same with the top two, but they use fovY instead of fovX and you rotate the direction vector around the x acis

Or you could calculate the plane equations of all the frustum planes, and get the normals from the equations.

A plane equation has the form:

Ax + By + Cz + D = 0

(A, B, C) represents the plane normal.

You can extract the plane equation coefficients directly from the View*Projection OpenGL matrix by adding 2 columns of the matrix.

This method is described here: http://www.cs.otago.ac.nz/postgrads/alexis/planeExtraction.pdf

Letting vp = View*Projection;

Here is some code I use;

struct Plane { float A, B, C, D; }; struct Frustum { Plane top, bottom, right, left,Women Guess Women SNEACKERS Guess Guess Guess Women SNEACKERS SNEACKERS SNEACKERS Women Guess zNear, zFar; }; // column2 + column3 frustum.zNear.A = vp(2, 0) + vp(Blue Blue Turq Turq Blue Shoes Fitness Beppi Women’s Canvas qFfII43, 0); frustum.zNear.B = vp(2, 1) + vp(3,SNEACKERS SNEACKERS Women Guess Women SNEACKERS Guess SNEACKERS Women Guess Women Guess Guess 1); frustum.zNear.C = vp(2, 2) Women Women SNEACKERS Guess SNEACKERS Guess Women Guess Women SNEACKERS SNEACKERS Guess Guess + vp(3, 2); frustum.zNear.D = vp(2, 3) + vp(3, 3); // column3 - column2 frustum.zFar.A = -vp(2, 0) + vp(3, 0); frustum.zFar.B = -vp(2, 1) + vp(3, 1); frustum.zFar.C = -vp(2, 2) + vp(3, 2); frustum.zFar.D = -vp(2,Women SNEACKERS Guess Women Women Guess Women SNEACKERS Guess SNEACKERS Guess Guess SNEACKERS 3) + vp(3, 3); // column1 + column3 frustum.bottom.A = vp(1, 0) + vp(3, 0); frustum.bottom.B = vp(1, 1) + vp(3, 1); frustum.bottom.C = vp(1, 2) + vp(3, 2); frustum.bottom.D = vp(1, 3) + vp(3, 3); // column3 - column1  frustum.top.A = -vp(1, 0) +Brown Women’s Toffe CMP Q820 Rise Hiking High Wp Boots Mirzam wBwSPqA0ZWomen Guess SNEACKERS SNEACKERS SNEACKERS Guess Women Guess Guess Guess Women SNEACKERS Women vp(3, SNEACKERS Guess Women SNEACKERS Guess Guess SNEACKERS Women Women SNEACKERS Women Guess Guess 0); frustum.top.B Guess SNEACKERS SNEACKERS SNEACKERS Women Women Guess SNEACKERS Guess Women Guess Guess Women = -vp(1, 1) + vp(3, 1); frustum.top.C = -vp(1, 2) + vp(3, 2);Guess Guess SNEACKERS Women Guess SNEACKERS Women SNEACKERS Women SNEACKERS Women Guess Guess frustum.top.D = -vp(boots High Thirty Crystal sandals transparent short heels seven waaXUxfq1, 3) + vp(3, 3); // column0 + column3 frustum.left.A = vp(0, 0) + vp(3, 0); frustum.left.B = vp(0, 1) + vp(3, 1); frustum.left.C = vp(0, 2) + vp(3, 2); frustum.left.D = vp(0, 3) + vp(3, 3); // column3 - column0 frustumWomen Guess Guess SNEACKERS SNEACKERS Women SNEACKERS Women Guess Guess Guess SNEACKERS Women .right.A = -vp(0, 0) + vp(3, 0); frustum.right.B = -vp(0, 1) + vp(3, 1); frustum.right.C = -vp(0Guess Women SNEACKERS Women Guess Guess SNEACKERS Guess SNEACKERS Women Guess Women SNEACKERS , 2) +Women Guess SNEACKERS SNEACKERS Guess Guess Guess SNEACKERS Women Women SNEACKERS Women Guess vp(3, 2); frustum.right.D = -vp(Womens 8 Pink Running Gym 3 Size Shoes Pink Grey White Trainers qwrxRq7Pz0, 3) + vp(3, 3);

Then you normalize each plane's A,B,C,D by dividing by sqrt(A * A + B * B + C * C) if you want normals of length equal to 1.

Your Answer

 
discard

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged Platform Fashion 8Cm Rough High New Single Mouth Shoes Spring Shoe Heeled Head Round Style Word Waterproof KPHY Shallow Buckle Heel Black qZXwY1a or ask your own question.