```/// LSU EE 7700-2 (Sp 08), Graphics Processors
//
/// Homework 1

/// Name:

// \$Id:\$

/// Instructions

// class procedures page, http://www.ece.lsu.edu/koppel/gp/proc.html

// For instructions on how to check out edit, compile, and debug, see
// the "Programming Homework Work Flow" entry on the procedures page,
// http://www.ece.lsu.edu/koppel/gp/proc.html.
//
// For those instructions you need to know that:
//
//  This assignment is at SVN URI https://svn.ece.lsu.edu/svn/gp/hw/2008/hw1
//
//  The assignment instructions are in file hw1.cc. (This file.)

// For the solutions to the problems below edit this file, even if
// it makes more sense to edit others (namely, coord.h). If it seems
// that coord.h must be edited, contact me.

// The main code is in routine render_hw1.

/// Problem 0

// Fill in your name in the comment above. Then build and test the
// program. It should display a tube similar to
// demo-4-lighting. Promptly resolve any problems, feel free to ask
// for help from Dr. Koppelman or others, especially on issues of
// missing libraries, and other setup problems.

/// Problem 1

// The large triangle has a flaw: There is a line extending out of
// the right side of the bottom of the triangle.

//  [ ] Fix the flaw.

// Note: The part of the code containing the flaw is the most
// time-critical in the rendering pipeline, which is why your attention
// is being focused there.

/// Problem 2

// Modify the code so that pressing "R" will rotate the tube by 15
// degrees in the y direction though the center of tube. Each R should
// rotate by another 15 degrees.

//  [ ] Modify to rotate by 15 degrees.

/// Problem 3

// Find a formula for render time in terms of vertices, pixels, and
// something related to triangles. The formula should be of the form:

//  t = t_tri n_tri + t_v n_v + t_p n_p,

// where n_tri is a count of something related to triangles, t_tri is
// the time per triangle (which you have determined), n_v is the
// number of vertices, and n_p is the number of pixels.

// Part of the problem is determining exactly what n_tri and n_p are. (There
// is only one reasonable interpretation of what n_v is.)

// The formula should work for the code in this file and should continue
// to work reasonably well if parameters such as pattern_levels change.

// Be sure to base this formula on the optimized version of the code.

//  [ ] Prepare a solution on paper (or pdf).

//  [ ] Show how well the solution works with the code with varying
//      values of pattern_width and pattern_levels.

//  [ ] Provide suggestions on where and how the rendering pipeline
//      code may be sped up.

#include <stdio.h>
#include <strings.h>
#include <stdlib.h>
#include <deque>

#include "frame_buffer.h"
#include "coord.h"

/// Vertex Object
//
// Holds coordinates plus color. In later examples will hold more
// information.
//
class pVertex : public pCoor {
public:
pVertex(float xp, float yp, float zp):pCoor(xp,yp,zp){};
pVertex(float xp, float yp, float zp, uint32_t color):
pCoor(xp,yp,zp){set_color(color);};
pVertex(pCoor c, pVect n, uint32_t color)
:pCoor(c),normal(n){set_color(color);}
pVertex():pCoor(){};
void set_color(uint32_t colorp)
{
color = colorp;
red = float( 0xff & ( color >> 16 ) );
green = float( 0xff & ( color >> 8 ) );
blue = float( 0xff & color );
}
float red, green, blue;
uint32_t color;
pVect normal;
};

/// Vertex List
//
// Declare vertex list types so that many vertices can easily be
// operated on.
//
typedef std::deque<pVertex*> pVertex_List;
typedef pVertex_List::iterator pVertex_Iterator;

/// Vertex Sort
//
// Sort three vertices at vertex list iterator position.
//
class pSortVertices {
public:
pSortVertices(pVertex_Iterator& ci)
{
rv_idx = 0;
for ( int i=0; i<3; i++ ) v[i] = ci[i];
swap(0,1); swap(0,2); swap(1,2);
}
operator pVertex& () { return *v[rv_idx++]; }
private:
void swap(int a, int b)
{
if ( v[a]->y <= v[b]->y ) return;
pVertex* const t = v[a];  v[a] = v[b];  v[b] = t;
}
pVertex* v[3];
int rv_idx;
};

int clampi(float valp, int min, int max)
{
const int val = (int) valp;
if ( val < min ) return min;
if ( val > max ) return max;
return val;
}

/// Interpolation Object
//
// Return x and y values on line connecting two points. Skips
// out-of-range values.
//
// Can be instantiated to advance in +x direction or +y direction.
//
class pInterpolate {
public:

pInterpolate(pVertex& v0, pVertex& v1, int ymin, int ymax)
{ set(v0, v1, ymin, ymax); }

void set(pVertex& v0, pVertex& v1, int ymin, int ymax)
{
const float y_range = v1.y - v0.y;
yi_last = ymax < int(v1.y) ? ymax : int(v1.y);
const float pre_y = float(ymin) - v0.y;
const bool scissor = pre_y > 0.0;
yi = scissor ? ymin : int(v0.y);
#define DELTA(item) \
d_##item = (float(v1.item) - v0.item) / y_range;            \
item = v0.item + ( scissor ? pre_y * d_##item : 0.0 );
DELTA(red); DELTA(green); DELTA(blue); DELTA(x); DELTA(z);
#undef DELTA
}

pInterpolate(pInterpolate& v0, pInterpolate& v1, int xmin, int xmax)
{
pInterpolate& vmin = v0.x < v1.x ? v0 : v1;
pInterpolate& vmax = v0.x < v1.x ? v1 : v0;
const float x_range = vmax.x - vmin.x;
xi_last = xmax < int(vmax.x) ? xmax : int(vmax.x);
const float pre_x = float(xmin) - vmin.x;
const bool scissor = pre_x > 0.0;
xi = scissor ? xmin : int(vmin.x);
#define DELTA(item) \
d_##item = (float(vmax.item) - vmin.item) / x_range;        \
item = vmin.item + ( scissor ? pre_x * d_##item : 0.0 );
DELTA(red); DELTA(green); DELTA(blue); DELTA(z);
#undef DELTA
}

bool keep_going_y() { return yi <= yi_last; }
bool keep_going_x() { return xi <= xi_last; }

{
red += d_red;  green += d_green;  blue += d_blue;  z += d_z;
}

uint32_t color()
{
return ( ( clampi(red,0,255) << 0 )
| ( clampi(green,0,255) << 8 )
| ( clampi(blue,0,255) << 16 ) );
}
float d_red, d_green, d_blue, d_x, d_z, red, green, blue, x, z;
int xi, xi_last, yi, yi_last;
};

// Add an unlighted tetrahedron to VTX_LIST at LOC of size SIZE.
//
void
insert_tetrahedron(pVertex_List& vtx_list, pCoor& loc, float size)
{
pCoor v0(loc.x,loc.y,loc.z);
pCoor v1(loc.x,loc.y-size,loc.z+size);
pCoor v2(loc.x-.866*size,loc.y-size,loc.z-0.5*size);
pCoor v3(loc.x+.866*size,loc.y-size,loc.z-0.5*size);
const int32_t c1 = 0x1ffffff, c2 = 0x100ff00;
pVect n;
# define TRI(va,vb,vc) \
n = cross(va,vb,vc); \
vtx_list.push_back( new pVertex(va,n,c1) ); \
vtx_list.push_back( new pVertex(vb,n,c2) ); \
vtx_list.push_back( new pVertex(vc,n,c2) );
TRI(v0,v1,v2); TRI(v0,v2,v3); TRI(v0,v3,v1);
# undef TRI
}

void
render_hw1(pFrame_Buffer &frame_buffer)
{
// Instantiate list of vertices.
//
pVertex_List vtx_list;

//
// Insert a tessellated tube in the vertex list.
//

// User Option: Use triangle normal or vertex normal.
//
static bool opt_triangle_normal = false;
if ( frame_buffer.keyboard_key == 'n' )
opt_triangle_normal = !opt_triangle_normal;
frame_buffer.fbprintf("Normals based on %s (use 'n' to change).\n",
opt_triangle_normal ? "triangle" : "vertex");

const float r = 2;                  // Tube radius.
const float x_shift = 0.4;          // Tube x offset.
const int pattern_levels = 50;      // Tube depth (z direction.)
const float pattern_width = 20;     // Triangle size (circumferential).
const float pattern_pitch_z = 0.25; // Triangle size (z axis).

float z = -1;
const uint32_t color_gold = 0xf9b237;    // LSU Spirit Gold
const uint32_t color_purple = 0x580da6;  // LSU Spirit Purple
const uint32_t color = color_gold;

// Get current time, intended for measuring performance of code.
// Time is in seconds since some arbitrary start time. (Today that
// start time might be New Years Day 1970 UTC, tomorrow it could be
// the time the program started running. So, it's only useful to take
// the difference between two values.  See pattern_loop_end below.)
//
const double pattern_loop_start = time_wall_fp();

// Outer Loop: z axis (down axis of tube).
//
for ( int i = 0; i < pattern_levels; i++ )
{
const float next_z = z - pattern_pitch_z;
const float last_z = z + pattern_pitch_z;
const float delta_theta = M_PI / pattern_width;
float theta = i & 1 ? delta_theta : 0;

// Inner Loop: around circumference of tube.
//
while ( theta < 4 * M_PI )
{
const float z1 = theta < 2 * M_PI ? next_z : last_z;

// For improved performance the tri functions would be pre-computed.

pVertex* const v0 =
new pVertex( x_shift + r * cos(theta), r * sin(theta), z, color );
if ( !opt_triangle_normal )
v0->normal = pVect(-cos(theta),-sin(theta),0);

theta += delta_theta;
pVertex* const v1 =
new pVertex( x_shift + r * cos(theta), r * sin(theta), z1, color);
if ( !opt_triangle_normal )
v1->normal = pVect(-cos(theta),-sin(theta),0);

theta += delta_theta;
pVertex* const v2 =
new pVertex( x_shift + r * cos(theta), r * sin(theta), z, color );
if ( !opt_triangle_normal )
v2->normal = pVect(-cos(theta),-sin(theta),0);

if ( opt_triangle_normal )
v0->normal = v1->normal = v2->normal = cross(*v0,*v1,*v2);

vtx_list.push_back( v0 );
vtx_list.push_back( v1 );
vtx_list.push_back( v2 );
}
z = next_z;
}

const double pattern_loop_end = time_wall_fp();
frame_buffer.fbprintf("The pattern loop took %.3f ms.\n",
( pattern_loop_end - pattern_loop_start ) * 1000 );

//
{
pVertex* const v0 = new pVertex( -2.5, 0, -3.2, color_purple );
pVertex* const v1 = new pVertex( 0, 5, -5, 0xff00 );
pVertex* const v2 = new pVertex( 1.5, 0.01, -3.2, 0xff );
v0->normal = v1->normal = v2->normal = cross(*v0,*v1,*v2);
vtx_list.push_back( v0 );
vtx_list.push_back( v1 );
vtx_list.push_back( v2 );
}

///
/// Light Location and Lighting Options
///

static bool opt_attenuation = true;
static bool opt_v_to_light = true;
static float opt_light_intensity = 2;
static pCoor light_location(x_shift + ( r - 0.1 ), 0, -3 );

// Adjust lighting options based on user input.
//
switch ( frame_buffer.keyboard_key ) {
case FB_KEY_LEFT: light_location.x -= 0.1; break;
case FB_KEY_RIGHT: light_location.x += 0.1; break;
case FB_KEY_UP: light_location.y += 0.1; break;
case FB_KEY_DOWN: light_location.y -= 0.1; break;
case FB_KEY_PAGE_DOWN: light_location.z += 0.2; break;
case FB_KEY_PAGE_UP: light_location.z -= 0.2; break;
case '-':case '_': opt_light_intensity *= 0.9; break;
case '+':case '=': opt_light_intensity *= 1.1; break;
case 'd': case 'D': opt_attenuation = !opt_attenuation; break;
case 'a': case 'A': opt_v_to_light = !opt_v_to_light; break;
default: break;
}

// User Messages  (Magically inserted into frame buffer.)
//
frame_buffer.fbprintf
("Lighting: Distance - %s,  Angle - %s  ('d' or 'a' to change).\n",
opt_attenuation ? "On" : "Off", opt_v_to_light ? "On" : "Off");
frame_buffer.fbprintf("Arrows, page up/down move light.\n");

// Insert marker (green tetrahedron) to show light location.
//
insert_tetrahedron(vtx_list,light_location,0.05);

///
/// Rendering Pipeline Starts Here
///

// Indicate to frame buffer simulator that code above is part of
// application and that code below is part of rendering pipeline.
//

frame_buffer.render_timing_start();

const int win_width = frame_buffer.get_width();
const int win_height = frame_buffer.get_height();
const int fb_size = win_width * win_height;
int32_t* const f_buffer = frame_buffer.get_buffer();

// Allocate and initialize a z buffer.
// (Note: Allocation only need be performed when size changes.)
//
float* const z_buffer = (float*) malloc( fb_size * sizeof(*z_buffer) );
for ( int i=0; i<fb_size; i++ ) z_buffer[i] = 1;

pMatrix_Translate center_eye(-1,-0.5,-3);

// Preserve aspect ratio when setting projection window height in frustrum.
const float aspect = float(win_width) / win_height;
pMatrix_Frustrum frustrum(1.6,1.6/aspect,1,5000);

pMatrix_Translate center_window(1,1,0);
pMatrix_Scale scale(win_width/2,win_height/2);

pMatrix transform_to_eye = center_eye;
pMatrix transform_to_viewport = scale * center_window * frustrum;

// Compute matrix needed to transform normals.
//
pMatrix normal_to_eye(transform_to_eye);
normal_to_eye.transpose(); normal_to_eye.invert3x3();

///
/// Transform Coordinates and Normals from Object Space to Eye Space
///
for ( pVertex_Iterator ci = vtx_list.begin(); ci < vtx_list.end(); ci++ )
{
pVertex& v = **ci;
v *= transform_to_eye;
v.normal *= normal_to_eye;
v.normal.normalize();
v.homogenize();
}

// Convert light location to object space.
//
pCoor light_location_e = transform_to_eye * light_location;

///
/// Apply Lighting to Vertices
///
for ( pVertex_Iterator ci = vtx_list.begin(); ci < vtx_list.end(); ci++ )
{
pVertex& v = **ci;
const bool opt_no_lighting = v.color & 0x1000000;
if ( opt_no_lighting ) continue;

// Compute vectors from vertex to light and to viewer.
//
pVect v_to_light(v,light_location_e);
pVect v_to_viewer(v,pCoor(0,0,0));

// Distance from vertex to light.
//
const float length = v_to_light.normalize();

// Projections:
//   1: vertex (normal) is facing light (or viewer).
//   0: vertex (normal) is orthogonal (90 degrees) from light.
//  -1: vertex (normal) is facing opposite direction of light.
//
const float dot_v_to_light = dot(v.normal,v_to_light);
const float dot_v_to_viewer = dot(v.normal,v_to_viewer);

// Dimming of light with distance.
//
// "Real" light dims with square of distance.
//
const float attenuation =
!opt_attenuation ? 1.0
: ( 0.5 * opt_light_intensity / ( length*length )
+ opt_light_intensity / length );

// Assume back side (-normal direction) is same color as front.
//
const float v_to_light_scale =
dot_v_to_viewer < 0 ? -dot_v_to_light : dot_v_to_light;

//
const float scale = attenuation
* ( !opt_v_to_light ? 1.0 : v_to_light_scale );

v.red *= scale;
v.green *= scale;
v.blue *= scale;
}

///
/// Transform Coordinates from Eye Space to Window Space
///
for ( pVertex_Iterator ci = vtx_list.begin(); ci < vtx_list.end(); ci++ )
{
pVertex& v = **ci;  // Get reference to current vertex
v *= transform_to_viewport;
v.homogenize();
}

/// Note: Code past this point should be identical to Demo 3.

///
/// Rasterize Primitives
///
for ( pVertex_Iterator ci = vtx_list.begin(); ci < vtx_list.end(); ci += 3 )
{
pSortVertices sort(ci); // Sort next 3 items in list.
pVertex& c0w = sort;    // Coordinate with smallest y.
pVertex& c1w = sort;
pVertex& c2w = sort;    // Coordinate with largest y.

// Instantiate interpolation objects.
//
// Each object instantiated with two coordinates and a valid
// range of y values.  The object will compute x and y along the
// line connecting those coordinates, skipping y values < 0 or
// >= win_width.
//
// Interpolation objects also interpolate z and color components.
//
pInterpolate interp_02(c0w,c2w,0,win_height-1);
pInterpolate interp_012(c0w,c1w,0,win_height-1);

// Compute position (index) in frame buffer of first row to be written.
//
int fb_line_idx = interp_02.yi * win_width;

// Outer Loop: Iterate from smallest y to largest y.
//
while ( interp_02.keep_going_y() )
{

// If point c1w reached then switch interp_012 to line
// connecting c1w and c2w.
//
if ( ! interp_012.keep_going_y() )
interp_012.set(c1w,c2w,0,win_height-1);

// Instantiate x-axis interpolation object using the two
// y-axis interpolation objects, interp_02 and interp_012.
// The new object will compute points on the line connecting
// the current position of interp_02 and interp_012.
//
pInterpolate interp_line(interp_02,interp_012,0,win_width-1);

// Inner Loop: Iterate along x axis.
//
while ( interp_line.keep_going_x() )
{
const int fb_idx = fb_line_idx + interp_line.xi;

// If z value to be written is smaller (in front of) z value
//
if ( z_buffer[ fb_idx ] > interp_line.z )
{
f_buffer[ fb_idx ] = interp_line.color();
z_buffer[ fb_idx ] = interp_line.z;
}

// Tell interpolation object to advance in x direction.
//
}

// Tell interpolation objects to advance in y direction.
//

// Advance the frame buffer index.
//
fb_line_idx += win_width;
}
}

// A paint routine is no place for a memory leak!
//
for ( pVertex_Iterator ci = vtx_list.begin(); ci < vtx_list.end(); ci++ )
delete *ci;
free(z_buffer);
}

int
main(int argc, char **argv)
{
pFrame_Buffer frame_buffer(argc,argv);
frame_buffer.show(render_hw1);
return 0;
}
```