# Homework #7: 3D Rendering Geometry Solution

\$30.00

Category:

## Description

Questions 1, 3, and 4 will walk you through the numerical computations for Lab 7.

Question 2 reviews the Gram-Schmidt orthogonalization we talked about in class.

1. A vertex of a polygonal model is located at (10; 15; 0) in the model’s object space. The model is rotated by 45 degrees around the y-axis and placed so that it is centered at (its origin maps to) position (30; 0; 40) in the world.

• Write out the model’s object-to-world transformation as a sequence of matrix operations. (You do not have to multiply out the matrices. You may also leave your answer in terms of trig functions.)

• Where is that vertex now in world coordinates?

1. A camera is located at position (25; 20; 5) in the 3D world and is looking at the point (25; 40; 25) so that the direction [0; 1; 0] points (roughly!) up.

• Use the process we covered in class (a 3D variant of Gram-Schmidt orthogonalization using cross products) to calculate the camera’s x, y, and z axis directions.

• Write this camera’s world-to-camera transformation as the composition of a rotation matrix and translation matrix. (You again do not have to multiply out this matrix.)
• What are the camera-space coordinates of the point pw = (5; 6; 7)?

1. A camera is located at position (20; 5; 40) and oriented so that it is pointing parallel to the x-z plane at an angle of 30 degrees off the z axis. (This is the basic setup for Labs 5–7.)

• Write this camera’s world-to-camera transformation using the composition of a 3D rotation matrix (around the y axis) and a translation matrix. (You again do not have to multiply out this matrix. You may also leave your answer in terms of trig functions.)
• What are the camera-space coordinates of the point pw = (5; 6; 7)?

1. A virtual camera has the following parameters:

vertical field of view of 60 degrees

aspect ratio of 16:9 (horizontal to vertical) near plane n = 10

far plane f = 1000

• What is the clip matrix for this camera?

• What are the clip-space coordinates of the camera-space point pc = (5; 5; 50)?

• Is this point pc = (5; 5; 50) within the view frustum of this camera? How can you tell directly from the clip-space coordinates without doing a division operation?

• What are the canonical coordinates of this point pc = (5; 5; 50)?

• If rendered to a high-definition display (1920 1080), what are the screen coordinates of this point?

2

error: Content is protected !!