/// LSU EE 4702-1 (Fall 2018), GPU Programming // /// Homework 3 -- SOLUTION // // Search for SOLUTION in this file to find solution code. /// Instructions // // Read the assignment: https://www.ece.lsu.edu/koppel/gpup/2018/hw03.pdf // // Modify the code in routine hw03_render. // // This file and hw03-shdr.cc will be collected. /// Purpose // // Demonstrate simulation of string modeled as point masses and springs /// What Code Does // Simulates a string of beads over a platform. The string is modeled // as point masses connected by springs with a long relaxed // length. The platform consists of tiles, some are purple-tinted // mirrors (showing a reflection of the ball), the others show the // course syllabus. /// Keyboard Commands // /// Object (Eye, Light, Ball) Location or Push // Arrows, Page Up, Page Down // Move object or push ball, depending on mode. // With shift key pressed, motion is 5x faster. // 'e': Move eye. // 'l': Move light. // 'b': Move head (first) ball. (Change position but not velocity.) // 'B': Push head ball. (Add velocity.) // /// Eye Direction // Home, End, Delete, Insert // Turn the eye direction. // Home should rotate eye direction up, End should rotate eye // down, Delete should rotate eye left, Insert should rotate eye // right. The eye direction vector is displayed in the upper left. /// Simulation Options // (Also see variables below.) // // '1' Set up scene 1. // '2' Set up scene 2. // 'p' Pause simulation. (Press again to resume.) // ' ' (Space bar.) Advance simulation by 1/30 second. // 'S- ' (Shift-space bar.) Advance simulation by one time step. // 'h' Freeze position of first (head) ball. (Press again to release.) // 't' Freeze position of last (tail) ball. (Press again to release.) // 's' Stop balls. // 'g' Turn gravity on and off. // 'F12' Write screenshot to file. /// Variables // Selected program variables can be modified using the keyboard. // Use "Tab" to cycle through the variable to be modified, the // name of the variable is displayed next to "VAR" on the bottom // line of green text. // 'Tab' Cycle to next variable. // '`' Cycle to previous variable. // '+' Increase variable value. // '-' Decrease variable value. // // VAR Spring Constant - Set spring constant. // VAR Air Resistance - Set air resistance. // VAR Light Intensity - The light intensity. // VAR Gravity - Gravitational acceleration. (Turn on/off using 'g'.) #define GL_GLEXT_PROTOTYPES #include <GL/gl.h> #include <GL/freeglut.h> #include <gp/util.h> #include <gp/coord.h> #include <gp/shader.h> #include <gp/pstring.h> #include <gp/misc.h> #include <gp/gl-buffer.h> #include <gp/texture-util.h> #include "shapes.h" /// /// Main Data Structures /// // // class World: All data about scene. class World; // Object Holding Ball State // class Ball { public: pCoor position; pVect velocity; float mass; float radius; bool contact; // Can be used for special effects. void push(pVect amt); void translate(pVect amt); void stop(); void freeze(); }; #include "hw03-graphics.cc" void World::init() { chain_length = 7; balls = new Ball[chain_length]; variable_control.insert_linear(opt_tryoutf,"Tryout F",0.1); opt_n_segs = 17; variable_control.insert(opt_n_segs,"Number of louver segments."); distance_relaxed = 30.0 / chain_length; opt_spring_constant = 1000; variable_control.insert(opt_spring_constant,"Spring Constant"); opt_gravity_accel = 9.8; opt_gravity = true; gravity_accel = pVect(0,-opt_gravity_accel,0); variable_control.insert(opt_gravity_accel,"Gravity"); opt_air_resistance = 0.001; variable_control.insert(opt_air_resistance,"Air Resistance"); world_time = 0; time_step_count = 0; last_frame_wall_time = time_wall_fp(); frame_timer.work_unit_set("Steps / s"); init_graphics(true); curr_setup = 1; ball_setup_1(); } void World::hw03_render(bool shadows) { // Homework 3 -- Problem 2, and maybe other problems. switch ( opt_shader ){ case SO_Fixed: sp_fixed->use(); break; case SO_Plain: sp_plain->use(); break; case SO_HW03: sp_hw03->use(); break; default: assert( false ); } pColor color_inside = 0.5 * color_salmon; pColor color_outside = 0.5 * color_chartreuse; if ( opt_shader != SO_Fixed ) { glUniform2i(3, opt_tryout_1, opt_tryout_2); glUniform1f(4, opt_tryoutf); } if ( opt_shader == SO_Plain ) { glColor3fv( color_outside ); } else { glDisable(GL_COLOR_MATERIAL); // Don't worry about re-enabling it. glMaterialfv( GL_FRONT, GL_AMBIENT_AND_DIFFUSE, color_inside ); glMaterialfv( GL_BACK, GL_AMBIENT_AND_DIFFUSE, color_outside ); } glEnable(GL_TEXTURE_2D); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D,texid_spiral_image); glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); glTexEnvi(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE); glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT); glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_REPEAT); for ( int i=2; i<chain_length; i++ ) { // Put ball structures and coordinates into convenient variables. // Ball* const b0 = &balls[i-2]; Ball* const b1 = &balls[i-1]; Ball* const b2 = &balls[i-0]; pCoor p0 = b0->position; pCoor p1 = b1->position; pCoor p2 = b2->position; // Compute location of triangle center. // pCoor ctr = (p0+p1+p2)/3; // Compute vectors from triangle center to each ball location .. // .. and put in array va. // pCoor pa[3] = {p0,p1,p2}; vector<pVect> va; for ( auto& p: pa ) va.emplace_back( ctr, p ); pNorm nz = cross(p0,p1,p2); const float vz_len = 0.1; pVect vz = vz_len * nz; const float delta_a = 0.8 / opt_n_segs; // Coordinate of previous position in triangular spiral. // pCoor pprev(0,0,0); /// SOLUTION -- Problem 2 // // Choose scaling factors for texture image. // const float tex_scale = 0.2; const float tex_ht = 2 * vz_len * tex_scale; // // Start the position within the texture image at the // upper-left corner. For Problem 2a the y component is // computed further below. For Problem 2b the y component is // computed in the fragment shader. // float tex_x = 0; /// SOLUTION -- Problem 2 and 3 // if ( opt_shader == SO_HW03 ) { // Send the spiral normal needed for Problem 3. // glUniform3fv(5, 1, nz); // Send the texture height used in Problem 2. // glUniform1f(6, tex_ht); } if ( opt_shader != SO_HW03 ) { /// Small Strips Rendering // // Render spiral using many triangle strips .. // .. one triangle strip for each louver. // for ( int j=0; j<opt_n_segs; j++ ) { // Distance from triangle center. // const float a = j * delta_a; // The vector to use for the current iteration. // pVect v = va[j%3]; // Compute point on bend of spiral, and its normal. // pCoor p = ctr + a * v; pNorm n = cross(pVect(pprev,p),vz); if ( j ) { /// SOLUTION -- Problem 2a // // Compute the length of the segment. This determines // how wide a piece of the texture image is used. // const float llen = pVect(p,pprev).mag(); /// SOLUTION -- Problem 2a // // Set the y coordinate based on the x coordinate. // const float tex_y = tex_ht * floor(tex_x); glBegin(GL_TRIANGLE_STRIP); glNormal3fv(n); /// SOLUTION -- Problem 2a -- provide texture coordinate. glTexCoord2f( tex_x, tex_y ); glVertex3fv(pprev + vz); /// SOLUTION -- Problem 2a -- provide texture coordinate. glTexCoord2f( tex_x, tex_y + tex_ht ); glVertex3fv(pprev - vz); /// SOLUTION -- Problem 2a // // Advance texture x component based on length of // segment. // tex_x += llen * tex_scale; /// SOLUTION -- Problem 2a -- provide texture coordinate. glTexCoord2f( tex_x, tex_y ); glVertex3fv(p + vz); /// SOLUTION -- Problem 2a -- provide texture coordinate. glTexCoord2f( tex_x, tex_y + tex_ht ); glVertex3fv(p - vz); glEnd(); } pprev = p; } } else { /// Large Strip Rendering // // Render entire spiral using one triangle strip. // glBegin(GL_TRIANGLE_STRIP); for ( int j=0; j<opt_n_segs; j++ ) { // Distance from triangle center. // const float a = j * delta_a; // The vector to use for the current iteration. // pVect v = va[j%3]; // Compute point on bend of spiral, and its normal. // pCoor p = ctr + a * v; pNorm n = cross(pVect(pprev,p),vz); glNormal3fv(n); /// SOLUTION -- Problem 2b // // The texture x component is computed in the same way // as for Problem 2a: it is incremented by the width of // the segment. // // However, the texture y component is either 0 or 1. // The fragment shader will compute the correct value // based on the value of the x component. /// SOLUTION -- Problem 2b -- provide texture coordinate. glTexCoord2f(tex_x,0); glVertex3fv(p + vz); /// SOLUTION -- Problem 2b -- provide texture coordinate. glTexCoord2f(tex_x,1); glVertex3fv(p - vz); /// SOLUTION -- Problem 2b // // Advance texture x component based on length of segment. // const float llen = pVect(p,pprev).mag(); tex_x += llen * tex_scale; pprev = p; } glEnd(); } } sp_fixed->use(); } /// /// Physical Simulation Code /// /// Initialize Simulation // void World::ball_setup_1() { /// Arrange balls almost vertically. pNorm dir(0.1,1,0.2); pCoor bottom_pos(12.5,distance_relaxed,-13.7); pNorm ax = dir.x ? pVect(-dir.y,dir.x,0) : pVect(0,-dir.z,dir.y); pVect leg_x = distance_relaxed * powf(0.75,0.5) * ax; pVect leg_y = distance_relaxed * 0.5f * dir; for ( int i=0; i<chain_length; i++ ) { Ball* const ball = &balls[chain_length-i-1]; ball->position = bottom_pos + i * leg_y + ( i & 1 ) * leg_x; ball->velocity = pVect(0,0,0); ball->radius = 0.1 * distance_relaxed; ball->mass = 4/3.0 * M_PI * pow(ball->radius,3); ball->contact = false; } opt_head_lock = true; opt_tail_lock = false; } void World::ball_setup_2() { /// Arrange and size balls to form a pendulum. // Desired position of first ball. // pCoor first_ball_pos(13.4,17.8,-9.2); // Desired distance between adjacent balls. // pVect ball_separation(distance_relaxed, 0, 0); // Points in +x direction. for ( int i=0; i<chain_length; i++ ) { Ball* const ball = &balls[i]; ball->position = first_ball_pos + i * ball_separation; ball->velocity = pVect(0,0,0); ball->radius = ( i == chain_length - 1 ? 0.6 : 0.3 ) * distance_relaxed; ball->mass = 4/3.0 * M_PI * pow(ball->radius,3); ball->contact = false; } opt_head_lock = true; } void World::ball_setup_3() { } void World::ball_setup_4() { } void World::ball_setup_5() { } /// Advance Simulation State by delta_t Seconds // void World::time_step_cpu(double delta_t) { time_step_count++; // /// Compute force and update velocity of each ball. // for ( int i=0; i<chain_length; i++ ) { Ball* const ball = &balls[i]; // Skip locked balls. // if ( opt_head_lock && i == 0 || opt_tail_lock && i == chain_length - 1 ) { ball->velocity = pVect(0,0,0); continue; } pVect force(0,0,0); // Gravitational Force // force += ball->mass * gravity_accel; // Spring Force from Neighbor Balls // for ( int direction: { -2, -1, +1, +2 } ) { const int n_idx = i + direction; // Compute neighbor index. // Skip this neighbor if neighbor doesn't exit. // if ( n_idx < 0 ) continue; if ( n_idx >= chain_length ) continue; Ball* const neighbor_ball = &balls[n_idx]; // Construct a normalized (Unit) Vector from ball to neighbor. // pNorm ball_to_neighbor( ball->position, neighbor_ball->position ); // Get distance between balls using pNorm member magnitude. // const float distance_between_balls = ball_to_neighbor.magnitude; // Compute by how much the spring is stretched (positive value) // or compressed (negative value). // const float spring_stretch = distance_between_balls - distance_relaxed; // Compute the speed of ball towards neighbor_ball. // pVect delta_v = neighbor_ball->velocity - ball->velocity; float delta_s = dot( delta_v, ball_to_neighbor ); // Determine whether spring is gaining energy (whether its length // is getting further from its relaxed length). // const bool gaining_e = ( delta_s > 0.0 ) == ( spring_stretch > 0 ); // Use a smaller spring constant when spring is loosing energy, // a quick and dirty way of simulating energy loss due to spring // friction. // const float spring_constant = gaining_e ? opt_spring_constant : opt_spring_constant * 0.7; force += spring_constant * spring_stretch * ball_to_neighbor; } // Update Velocity // // This code assumes that force on ball is constant over time // step. This is clearly wrong when balls are moving with // respect to each other because the springs are changing // length. This inaccuracy will make the simulation unstable // when spring constant is large for the time step. // ball->velocity += ( force / ball->mass ) * delta_t; // Air Resistance // const double fs = pow(1+opt_air_resistance,-delta_t); ball->velocity *= fs; } /// /// Update Position of Each Ball /// for ( int i=0; i<chain_length; i++ ) { Ball* const ball = &balls[i]; // Update Position // // Assume that velocity is constant. // ball->position += ball->velocity * delta_t; // Possible Collision with Platform // // Skip if collision impossible. // if ( !platform_collision_possible(ball->position) ) continue; if ( ball->position.y >= 0 ) continue; // Reflect y (vertical) component of velocity, with a reduction // due to energy lost in the collision. // if ( ball->velocity.y < 0 ) ball->velocity.y = - 0.9 * ball->velocity.y; } } bool World::platform_collision_possible(pCoor pos) { // Assuming no motion in x or z axes. // return pos.x >= platform_xmin && pos.x <= platform_xmax && pos.z >= platform_zmin && pos.z <= platform_zmax; } /// External Modifications to State // // These allow the user to play with state while simulation // running. // Move the ball. // void Ball::translate(pVect amt) {position += amt;} // Add velocity to the ball. // void Ball::push(pVect amt) {velocity += amt;} // Set the velocity to zero. // void Ball::stop() {velocity = pVect(0,0,0); } // Set the velocity and rotation (not yet supported) to zero. // void Ball::freeze() {velocity = pVect(0,0,0); } void World::balls_translate(pVect amt,int b){balls[b].translate(amt);} void World::balls_push(pVect amt,int b){balls[b].push(amt);} void World::balls_translate(pVect amt) { for(int i=0;i<chain_length;i++)balls[i].translate(amt);} void World::balls_push(pVect amt) { for(int i=0;i<chain_length;i++)balls[i].push(amt);} void World::balls_stop() { for(int i=0;i<chain_length;i++)balls[i].stop();} void World::balls_freeze(){balls_stop();} void World::frame_callback() { // This routine called whenever window needs to be updated. const double time_now = time_wall_fp(); if ( !opt_pause || opt_single_frame || opt_single_time_step ) { /// Advance simulation state. // Amount of time since the user saw the last frame. // const double wall_delta_t = time_now - last_frame_wall_time; const double time_step_duration = 0.0001; // Compute amount by which to advance simulation state for this frame. // const double duration = opt_single_time_step ? time_step_duration : opt_single_frame ? 1/30.0 : wall_delta_t; const double world_time_target = world_time + duration; while ( world_time < world_time_target ) { time_step_cpu(time_step_duration); world_time += time_step_duration; } // Reset these, just in case they were set. // opt_single_frame = opt_single_time_step = false; } last_frame_wall_time = time_now; render(); } int main(int argv, char **argc) { pOpenGL_Helper popengl_helper(argv,argc); World world(popengl_helper); # ifdef __OPTIMIZE__ glDisable(GL_DEBUG_OUTPUT); # else glEnable(GL_DEBUG_OUTPUT); # endif glDebugMessageControl(GL_DONT_CARE,GL_DONT_CARE, GL_DEBUG_SEVERITY_NOTIFICATION,0,NULL,false); popengl_helper.rate_set(30); popengl_helper.display_cb_set(world.frame_callback_w,&world); }