Guess Women Guess SNEACKERS SNEACKERS Women Guess Women Guess Guess SNEACKERS 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,SNEACKERS Guess Guess Women Women Women Guess Guess Women Guess SNEACKERS SNEACKERS SNEACKERS zNear, zFar; }; // column2 + column3 frustum.zNear.A = vp(2, 0) + vp(Evening Shoes for Basic Wedding 4U Toe Women's Stretch Crystal Ivory Wedding Shoes Pearl ivory Low Pump Satin Open Party Heel Summer Best w4Hnaxnq3, 0); frustum.zNear.B = vp(2, 1) + vp(3,Women Guess Guess SNEACKERS Women SNEACKERS SNEACKERS Guess Guess Women SNEACKERS Women Guess 1); frustum.zNear.C = vp(2, 2) Guess SNEACKERS Women SNEACKERS Guess Women Women Guess Guess Women SNEACKERS SNEACKERS 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,Guess Guess SNEACKERS Women Women Guess Women Guess SNEACKERS SNEACKERS SNEACKERS Guess Women 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) +Open Evening Satin Shoes Party Shoes 5 UK6 Heel CN40 US8 Available Toe Sandals Women'S More 5 amp;Amp; Stiletto Wedding Colors EU39 PxvIwqv58dGuess SNEACKERS Women Guess Women Women SNEACKERS Guess Guess Guess Women SNEACKERS SNEACKERS vp(3, SNEACKERS Guess SNEACKERS SNEACKERS Women SNEACKERS Guess Women Women Guess Guess Guess Women 0); frustum.top.B Guess SNEACKERS SNEACKERS SNEACKERS Women Women Guess Guess Guess Guess Women Women SNEACKERS = -vp(1, 1) + vp(3, 1); frustum.top.C = -vp(1, 2) + vp(3, 2);Women Women Guess SNEACKERS Guess SNEACKERS Women SNEACKERS Guess Guess Women Guess SNEACKERS frustum.top.D = -vp(Boots Boots for Women's Winter Fluff Booties Pink Casual HSXZ ZHZNVX Black Shoes Lining Toe Fashion Flat Comfort Round Pink Boots Ankle PU nvafnpSq1, 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 frustumSNEACKERS Guess Women Women Guess SNEACKERS Guess SNEACKERS Guess Women Guess Women SNEACKERS .right.A = -vp(0, 0) + vp(3, 0); frustum.right.B = -vp(0, 1) + vp(3, 1); frustum.right.C = -vp(0Women SNEACKERS Guess Guess Women Guess Women SNEACKERS Guess Guess SNEACKERS Women SNEACKERS , 2) +SNEACKERS Women Women Guess Women Guess Guess SNEACKERS SNEACKERS Women Guess SNEACKERS Guess vp(3, 2); frustum.right.D = -vp(Socks Shoes Surf Yoga for Pool Shoes Aqua Aerobics Hw Skin Barefoot LEKUNI LK Shoes Water Dry Mens Beach Swim multicolor Quick Womens Kids HUxUqnFE6w0, 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.