[SOLVED] CS770/870 Assignment 8 C/C

CS770/870 Assignment 8

• Out: Tuesday, November 5th.

•  Due: Thursday, November 14th.

Overview

In this assignment, you will write a ray tracer that uses only primary rays (no reflected, refracted or shadow rays). You should be able to render spheres, triangles, and cylinders.

For a 10% bonus, implement shadow rays.

The Scene

Your rendering should be based on a scene, which is described by the following information:

• one or more materials

• a list of shapes

• a list of lights

• a camera

Pseudocode

You are free to implement the ray tracer any way you see fit, but I suggest you follow this pseudocode:

foreach pixel (image) {

ray = new_ray (pixel, pixel-eye)

pixel’s color = ray_color (ray, scene)

}

ray_color (ray, scene) {

hit = first_hit (ray, scene)

bj = hit.shape

return glossy_color (ray, hit, obj, scene)

}

first_hit (ray, scene) {

list = (empty)

foreach shape (scene) {

if (ray intersects shape at location) {

hit = hitpoint(location, N, shape)

list.append(hit)

}

}

return list.getMinimum()

}

glossy_color (ray, hit, obj, scene) {

lights = scene.light_list

color = (0 0 0)

foreach light (lights) {

color += local_illum (ray.dir, hit.normal, light.dir,

obj.material, light.color)

}

color += obj.material.ambient_color * ambient_light

return color

}

local_illum (rayDir, N, L, mat, I) {

V = -rayDir

R = mirror_direction (L, N)

kd = mat.diffuse_color

ks = mat.specular_color

n = mat.glossiness

return I * (kd * N dot L + ks * (R dot V)^n)

}

mirror_direction (L, N) {

return 2(N dot L)*N – L

}

C++ Classes

This assignment extends the previous one. The new features include:

• Instead of a vec3 color, each Shape now has an associated Material. The Material class (already implemented) has information for calculating a color using the Phong illumination model:

– ambient reflectance

– difuse reflectance

– specular reflectance

– shininess exponent

• The Hit class now has pointer to Material insted of a simple vec3 color.  Its .set () method has changed accordingly (already implemented).

• The Light class describes a point light source, with this information (already implemented):

– position

– color

• The Shape class and its children Triangle, Sphere and Cylinder all have a Material field too.

• The Camera class is new. It has these fields (all public) (already implemented):

– _eye : eye position

– _lookat : where the camera is looking at

– _up : which way is “up” in the world

– _clip_Left, _clip_Right, _clip_Bottom, _clip_Top, and _clip_Near : these position the image rect- angle.

– _ambient_fraction : how much each light contributes to the over-all ambient light.

• The Caster class has several changes:

– It now has a _camera instance variable. This is a Camera object, which you’ll use to re-compute the VCS→ WCS matrix.

– The method that should update the VCS→ WCS matrix is now called camera_did_move ().

– The ray_color () method should implement the pseudocode above.

– The glossy_color () method should compute the color at the given hit point, taking all the light sources into account, and also the ambient light color.

– The local_illumination () method computes the contribution of ONE light to the hit point.

– The mirror_direction () method computes the reflection R vector, based on the vector L towards the light, and the vector N normal to the hit surface.

– The hits_something() method should return true/false if the given ray hits some object. It’s used for shadow rays. You should call it from ray_color () if_shadowing is‘true.

– The read_scene () method replaces the init_scene (). It reads a scene description from a file (already implemented).

• The Tokenize r class will read a file, and report whitespace-separated tokens.  It has these methods (already implemented):

– next_string() : returns the next token.

– next_number () : returns the next token, converted to a float (may throw an exception).

– match (s ) : reads the next token, and throws an exception if it doesn’t match s.

– eof () : returns true at end of file.

– file_position() : returns a string describing the current line number in the file.

• The Scene_Reader class handles reading the scene description. It includes these methods:

– read_sphere() : reads information for a sphere, and returns a pointer to a new Sphere object (already implemented).

– read_triangle() : reads information for a triangle, and returns a pointer to a new Triangle object. NOT COMPLETE.

– read_cylinder() : reads information for a cylinder aligned with they axis, and returns a pointer to a new Cylinder object. NOT COMPLETE.

– read_material () : reads information for a surface material, and returns a Material object. NOT COM– PLETE.

– read_light() : reads information for a point light source, and returns a Light object. NOT COMPLETE.

– read_camera () : reads information for the camera, and returns a Camera object. NOT COMPLETE.

– read_vec3 () reads three floats, and returns a vec3 (already implemented).

– find_named_material () : given a vector of Materials, and a name, returns the Material that matches the name (already implemented).

Controls

The following keyboard controls are implemented in the Caster_Controller class (which you don’t have to change):

•  UP  /  DOWN  arrow: move eye up/down, keeping look-at point fixed

•  LEFT   /   RIGHT  arrow : move eye le/right, keeping look-at point fixed

• Shift+UP  /  Shift+DOWN  arrow: move eye forward/backward.

• R  /  Shift+R : decrease/increase the resolution

• C : output the current camera position.

• S : toggle the _shadowing flag.

Additional Information

I’ve prepared additional information files:

• data-format .pdf: syntax specifications for the scene files.

• illumination .pdf : details on the Phong local illumination.

• rt-faq.pdf : other frequently-asked questions.

Expected Output

The program caster expects a command-line argument, which is a scene file. If you type

caster scene/pyramid.txt

on the command line, you should see this:

If you type

caster  scene/snowman .txt

on the command line (and have implemented shadows), you should see this:

If you type

caster scene/snowman-1light.txt

on the command line (and have implemented shadows), you should see this:

Submission

When you are done, go to the mycourses, find the course, upload all the files that you changed (especially caster .cpp, triangle.cpp, sphere.cpp, cylinder.cpp, and scene_ reader .cpp),and click “Submit”.