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Add OpenGL ES variant of Boing demo.

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Mike Gorchak 2024-07-17 11:05:30 -04:00
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/*****************************************************************************
* Title: OpenGL ES Boing
* Desc: Tribute to Amiga Boing.
* Author: Jim Brooks <gfx@jimbrooks.org>
* Original Amiga authors were R.J. Mical and Dale Luck.
* GLFW conversion by Marcus Geelnard
* OpenGL ES port by Mike Gorchak
* Notes: - 360' = 2*PI [radian]
*
* - Distances between objects are created by doing a relative
* Z translations.
*
* - Although OpenGL ES enticingly supports alpha-blending,
* the shadow of the original Boing didn't affect the color
* of the grid.
*
* - [Marcus] Changed timing scheme from interval driven to frame-
* time based animation steps (which results in much smoother
* movement)
*
* History of Amiga Boing:
*
* Boing was demonstrated on the prototype Amiga (codenamed "Lorraine") in
* 1985. According to legend, it was written ad-hoc in one night by
* R. J. Mical and Dale Luck. Because the bouncing ball animation was so fast
* and smooth, attendees did not believe the Amiga prototype was really doing
* the rendering. Suspecting a trick, they began looking around the booth for
* a hidden computer or VCR.
*****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#define GLAD_GLES2_IMPLEMENTATION
#include <glad/gles2.h>
#define GLFW_INCLUDE_NONE
#include <GLFW/glfw3.h>
#include <linmath.h>
/*****************************************************************************
* Various declarations and macros
*****************************************************************************/
/* Draw ball, or its shadow */
typedef enum
{
DRAW_BALL,
DRAW_BALL_SHADOW
} DRAW_BALL_ENUM;
/* Prototypes */
void init(void);
void display(void);
void reshape(GLFWwindow* window, int w, int h);
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods);
void mouse_button_callback(GLFWwindow* window, int button, int action, int mods);
void cursor_position_callback(GLFWwindow* window, double x, double y);
void GenerateBoingBall(void);
void GenerateGrid(void);
void DrawBoingBall(DRAW_BALL_ENUM drawBallHow);
void DrawGrid(void);
void BounceBall(float dt);
#define RADIUS 70.0f
#define STEP_LONGITUDE 22.5f /* 22.5 makes 8 bands like original Boing */
#define STEP_LATITUDE 22.5f
#define DIST_BALL (RADIUS * 2.0f + RADIUS * 0.1f)
#define VIEW_SCENE_DIST (DIST_BALL * 3.0f + 200.0f) /* distance from viewer to middle of boing area */
#define GRID_SIZE (RADIUS * 4.5f) /* length (width) of grid */
#define BOUNCE_HEIGHT (RADIUS * 2.1f)
#define BOUNCE_WIDTH (RADIUS * 2.1f)
#define SHADOW_OFFSET_X -20.0f
#define SHADOW_OFFSET_Y 10.f
#define SHADOW_OFFSET_Z 0.0f
#define WALL_L_OFFSET 0.0f
#define WALL_R_OFFSET 5.0f
/* Animation speed (50.0 mimics the original GLUT demo speed) */
#define ANIMATION_SPEED 50.0f
/* Maximum allowed delta time per physics iteration */
#define MAX_DELTA_T 0.02f
/* Global vars */
int windowed_xpos, windowed_ypos, windowed_width, windowed_height;
int width, height;
int override_pos = GLFW_FALSE;
float deg_rot_y = 0.0f;
float deg_rot_y_inc = 2.0f;
float cursor_x = 0.0f;
float cursor_y = 0.0f;
float ball_x = -RADIUS;
float ball_y = -RADIUS;
float ball_x_inc = 1.0f;
float ball_y_inc = 2.0f;
float t;
float t_old = 0.0f;
float dt;
/* Random number generator */
#ifndef RAND_MAX
#define RAND_MAX 4095
#endif
static mat4x4 projection;
static mat4x4 modelview_orig;
static mat4x4 modelview;
static mat4x4 mvp;
static vec3* ball_color1_vertices = NULL;
static vec3* ball_color2_vertices = NULL;
static vec3* grid_vertices = NULL;
static vec3 color1 = {0.8f, 0.1f, 0.1f}; /* reddish */
static vec3 color2 = {0.95f, 0.95f, 0.95f}; /* almost white */
static vec3 color_shadow = {0.35f, 0.35f, 0.35f}; /* dark grey */
static vec3 grid_color = {0.6f, 0.1f, 0.6f}; /* purple */
static int facet_array_size = 0;
static int grid_array_size = 0;
static GLuint buffer;
static GLuint program;
static GLuint mvp_matrix_loc = -1;
static GLuint vertex_color_loc = -1;
static GLuint vertex_attr_index = -1;
/*****************************************************************************
* Truncate a degree.
*****************************************************************************/
float TruncateDeg(float deg)
{
if (deg >= 360.0f)
return (deg - 360.0f);
else
return deg;
}
/*****************************************************************************
* Convert a degree (360-based) into a radian.
* 360' = 2 * PI
*****************************************************************************/
float deg2rad(float deg)
{
return deg / 360.0f * (2.0f * M_PI);
}
/*****************************************************************************
* 360' sin().
*****************************************************************************/
float sin_deg(float deg)
{
return sin(deg2rad(deg));
}
/*****************************************************************************
* 360' cos().
*****************************************************************************/
float cos_deg(float deg)
{
return cos(deg2rad(deg));
}
/*****************************************************************************
* init_shaders()
*****************************************************************************/
static int init_shaders(void)
{
GLenum error;
GLuint vertex_shader, fragment_shader;
char log[8192];
GLsizei len;
GLint processing_done = GL_TRUE;
error = glGetError();
const char *vtx_shdr_src =
"attribute vec3 vertex_position; \n"
" \n"
"uniform mat4 mvp_matrix; \n"
"uniform vec4 vertex_color; \n"
" \n"
"varying vec4 fs_color; \n"
" \n"
"void main() \n"
"{ \n"
" fs_color = vertex_color; \n"
" gl_Position = mvp_matrix * vec4(vertex_position, 1.0); \n"
"} \n";
const char *frg_shdr_src =
"varying vec4 fs_color; \n"
" \n"
"void main(void) \n"
"{ \n"
" gl_FragColor = fs_color; \n"
"} \n";
program = glCreateProgram();
vertex_shader = glCreateShader(GL_VERTEX_SHADER);
glAttachShader(program, vertex_shader);
glShaderSource(vertex_shader, 1, (const char**)&vtx_shdr_src, NULL);
glCompileShader(vertex_shader);
glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &processing_done);
if (processing_done != GL_TRUE)
{
glGetShaderInfoLog(vertex_shader, sizeof(log), &len, log);
fprintf(stderr, "Vertex Shader: %s", log);
return -1;
}
fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
glAttachShader(program, fragment_shader);
glShaderSource(fragment_shader, 1, (const char**)&frg_shdr_src, NULL);
glCompileShader(fragment_shader);
glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &processing_done);
if (processing_done != GL_TRUE)
{
glGetShaderInfoLog(fragment_shader, sizeof(log), &len, log);
fprintf(stderr, "Fragment Shader: %s", log);
return -1;
}
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &processing_done);
if (processing_done != GL_TRUE)
{
glGetProgramInfoLog(program, sizeof(log), &len, log);
fprintf(stderr, "Linker: %s", log);
return -1;
}
glUseProgram(program);
mvp_matrix_loc = glGetUniformLocation(program, "mvp_matrix");
if ((mvp_matrix_loc == -1))
{
fprintf(stderr, "Can't locate location of MVP matrix uniform!\n");
return -1;
}
vertex_color_loc = glGetUniformLocation(program, "vertex_color");
if (vertex_color_loc == -1)
{
fprintf(stderr, "Can't locate location of fog color uniform!\n");
return -1;
}
vertex_attr_index = glGetAttribLocation(program, "vertex_position");
if (vertex_attr_index == -1)
{
fprintf(stderr, "Can't locate location of vertex attribute!\n");
return -1;
}
/* We do not change VBO and use index offsets to the array elements */
glEnableVertexAttribArray(vertex_attr_index);
glVertexAttribPointer(vertex_attr_index, 3, GL_FLOAT, GL_FALSE, 0, (const GLvoid*)(uintptr_t)0);
error = glGetError();
if (error != GL_NO_ERROR)
{
fprintf(stderr, "GL Error: 0x%04X in shaders setup\n", error);
return -1;
}
return 0;
}
/*****************************************************************************
* init()
*****************************************************************************/
void init(void)
{
int offset = 0;
/* Clear background. */
glClearColor(0.55f, 0.55f, 0.55f, 0.0f);
/* Generate initial modelview matrix */
vec3 eye = {0.0f, 0.0f, VIEW_SCENE_DIST};
vec3 center = {0.0f, 0.0f, 0.0f};
vec3 up = {0.0f, -1.0f, 0.0f};
mat4x4_look_at(modelview_orig, eye, center, up);
GenerateBoingBall();
GenerateGrid();
/* Setup VBO */
glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, facet_array_size + facet_array_size + grid_array_size,
NULL, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, offset, facet_array_size, ball_color1_vertices);
offset += facet_array_size;
glBufferSubData(GL_ARRAY_BUFFER, offset, facet_array_size, ball_color2_vertices);
offset += facet_array_size;
glBufferSubData(GL_ARRAY_BUFFER, offset, grid_array_size, grid_vertices);
offset += grid_array_size;
/* We don't need vertices in a heap, they were uploaded as VBO */
free(ball_color1_vertices);
free(ball_color2_vertices);
free(grid_vertices);
init_shaders();
}
/*****************************************************************************
* display()
*****************************************************************************/
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
DrawBoingBall(DRAW_BALL_SHADOW);
DrawGrid();
DrawBoingBall(DRAW_BALL);
}
/*****************************************************************************
* reshape()
*****************************************************************************/
void reshape(GLFWwindow* window, int w, int h)
{
width = w;
height = h;
glViewport(0, 0, (GLsizei)w, (GLsizei)h);
mat4x4_perspective(projection, 2.0f * (float)atan2(RADIUS, 200.0f), (float)w / (float)h, 1.0f, VIEW_SCENE_DIST);
}
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if (action != GLFW_PRESS)
return;
if (key == GLFW_KEY_ESCAPE && mods == 0)
glfwSetWindowShouldClose(window, GLFW_TRUE);
if ((key == GLFW_KEY_ENTER && mods == GLFW_MOD_ALT) ||
(key == GLFW_KEY_F11 && mods == GLFW_MOD_ALT))
{
if (glfwGetWindowMonitor(window))
{
glfwSetWindowMonitor(window, NULL,
windowed_xpos, windowed_ypos,
windowed_width, windowed_height, 0);
}
else
{
GLFWmonitor* monitor = glfwGetPrimaryMonitor();
if (monitor)
{
const GLFWvidmode* mode = glfwGetVideoMode(monitor);
glfwGetWindowPos(window, &windowed_xpos, &windowed_ypos);
glfwGetWindowSize(window, &windowed_width, &windowed_height);
glfwSetWindowMonitor(window, monitor, 0, 0, mode->width, mode->height, mode->refreshRate);
}
}
}
}
static void set_ball_pos(float x, float y)
{
ball_x = (width / 2) - x;
ball_y = y - (height / 2);
}
void mouse_button_callback(GLFWwindow* window, int button, int action, int mods)
{
if (button != GLFW_MOUSE_BUTTON_LEFT)
return;
if (action == GLFW_PRESS)
{
override_pos = GLFW_TRUE;
set_ball_pos(cursor_x, cursor_y);
}
else
{
override_pos = GLFW_FALSE;
}
}
void cursor_position_callback(GLFWwindow* window, double x, double y)
{
cursor_x = (float)x;
cursor_y = (float)y;
if (override_pos)
set_ball_pos(cursor_x, cursor_y);
}
/*****************************************************************************
* Generate the Boing ball.
*
* The Boing ball is sphere in which each facet is a rectangle.
* Facet colors alternate between red and white.
* The ball is built by stacking latitudinal circles. Each circle is composed
* of a widely-separated set of points, so that each facet is noticeably large.
*****************************************************************************/
void GenerateBoingBall(void)
{
/* degree of longitude */
float lon_deg;
float lat_deg;
int vertex_idx_c1 = 0;
int vertex_idx_c2 = 0;
bool colorToggle = 0;
/* "ne" means south-east, so on */
vec3 vert_ne;
vec3 vert_nw;
vec3 vert_sw;
vec3 vert_se;
/* "/ 2" - half facets of one color */
/* "* 6" - 6 vertices per facet (two triangles) */
facet_array_size = (int)((180.0f / STEP_LONGITUDE) * (360.0f / STEP_LATITUDE) / 2) * 6 * sizeof(vec3);
ball_color1_vertices = calloc(1, facet_array_size);
ball_color2_vertices = calloc(1, facet_array_size);
if ((ball_color1_vertices == NULL) || (ball_color2_vertices == NULL))
{
fprintf(stderr, "Can't allocate memory for ball vertices!\n");
glfwTerminate();
exit(EXIT_FAILURE);
}
/*
* Build a faceted latitude slice of the Boing ball,
* stepping same-sized vertical bands of the sphere.
*/
for (lon_deg = 0; lon_deg < 180; lon_deg += STEP_LONGITUDE)
{
/*
* Iterate through the points of a latitude circle.
* A latitude circle is a 2D set of X,Z points.
*/
for (lat_deg = 0; lat_deg <= (360 - STEP_LATITUDE); lat_deg += STEP_LATITUDE)
{
/* Assign each Y. */
vert_ne[1] = vert_nw[1] = (float) cos_deg((lon_deg + STEP_LONGITUDE)) * RADIUS;
vert_sw[1] = vert_se[1] = (float) cos_deg(lon_deg) * RADIUS;
/*
* Assign each X,Z with sin,cos values scaled by latitude radius indexed by longitude.
* Eg, long=0 and long=180 are at the poles, so zero scale is sin(longitude),
* while long=90 (sin(90)=1) is at equator.
*/
vert_ne[0] = (float)cos_deg(lat_deg ) * (RADIUS * (float)sin_deg(lon_deg + STEP_LONGITUDE));
vert_se[0] = (float)cos_deg(lat_deg ) * (RADIUS * (float)sin_deg(lon_deg ));
vert_nw[0] = (float)cos_deg(lat_deg + STEP_LATITUDE) * (RADIUS * (float)sin_deg(lon_deg + STEP_LONGITUDE));
vert_sw[0] = (float)cos_deg(lat_deg + STEP_LATITUDE) * (RADIUS * (float)sin_deg(lon_deg ));
vert_ne[2] = (float)sin_deg(lat_deg ) * (RADIUS * (float)sin_deg(lon_deg + STEP_LONGITUDE));
vert_se[2] = (float)sin_deg(lat_deg ) * (RADIUS * (float)sin_deg(lon_deg ));
vert_nw[2] = (float)sin_deg(lat_deg + STEP_LATITUDE) * (RADIUS * (float)sin_deg(lon_deg + STEP_LONGITUDE));
vert_sw[2] = (float)sin_deg(lat_deg + STEP_LATITUDE) * (RADIUS * (float)sin_deg(lon_deg ));
/*
* Color this polygon with red or white. Replace polygons with
* triangles to perform a batch draw operation.
*/
if (colorToggle)
{
memcpy(ball_color1_vertices[vertex_idx_c1 + 0], vert_ne, sizeof(vec3)); /* V0 */
memcpy(ball_color1_vertices[vertex_idx_c1 + 1], vert_nw, sizeof(vec3)); /* V1 */
memcpy(ball_color1_vertices[vertex_idx_c1 + 2], vert_sw, sizeof(vec3)); /* V2 */
memcpy(ball_color1_vertices[vertex_idx_c1 + 3], vert_ne, sizeof(vec3)); /* V0 */
memcpy(ball_color1_vertices[vertex_idx_c1 + 4], vert_sw, sizeof(vec3)); /* V2 */
memcpy(ball_color1_vertices[vertex_idx_c1 + 5], vert_se, sizeof(vec3)); /* V3 */
vertex_idx_c1 += 6;
}
else
{
memcpy(ball_color2_vertices[vertex_idx_c2 + 0], vert_ne, sizeof(vec3)); /* V0 */
memcpy(ball_color2_vertices[vertex_idx_c2 + 1], vert_nw, sizeof(vec3)); /* V1 */
memcpy(ball_color2_vertices[vertex_idx_c2 + 2], vert_sw, sizeof(vec3)); /* V2 */
memcpy(ball_color2_vertices[vertex_idx_c2 + 3], vert_ne, sizeof(vec3)); /* V0 */
memcpy(ball_color2_vertices[vertex_idx_c2 + 4], vert_sw, sizeof(vec3)); /* V2 */
memcpy(ball_color2_vertices[vertex_idx_c2 + 5], vert_se, sizeof(vec3)); /* V3 */
vertex_idx_c2 += 6;
}
colorToggle = ! colorToggle;
}
/* Toggle color so that next band will opposite red/white colors than this one. */
colorToggle = ! colorToggle;
}
}
/*****************************************************************************
* Bounce the ball.
*****************************************************************************/
void BounceBall(float delta_t)
{
float sign;
float deg;
if (override_pos)
return;
/* Bounce on walls */
if (ball_x > (BOUNCE_WIDTH / 2 + WALL_R_OFFSET))
{
ball_x_inc = -0.5f - 0.75f * (float)rand() / (float)RAND_MAX;
deg_rot_y_inc = -deg_rot_y_inc;
}
if (ball_x < -(BOUNCE_HEIGHT / 2 + WALL_L_OFFSET))
{
ball_x_inc = 0.5f + 0.75f * (float)rand() / (float)RAND_MAX;
deg_rot_y_inc = -deg_rot_y_inc;
}
/* Bounce on floor / roof */
if (ball_y > BOUNCE_HEIGHT / 2)
{
ball_y_inc = -0.75f - 1.0f * (float)rand() / (float)RAND_MAX;
}
if (ball_y < -BOUNCE_HEIGHT / 2 * 0.85)
{
ball_y_inc = 0.75f + 1.0f * (float)rand() / (float)RAND_MAX;
}
/* Update ball position */
ball_x += ball_x_inc * ((float)delta_t * ANIMATION_SPEED);
ball_y += ball_y_inc * ((float)delta_t * ANIMATION_SPEED);
/* Simulate the effects of gravity on Y movement. */
if (ball_y_inc < 0) sign = -1.0; else sign = 1.0;
deg = (ball_y + BOUNCE_HEIGHT / 2) * 90 / BOUNCE_HEIGHT;
if (deg > 80) deg = 80;
if (deg < 10) deg = 10;
ball_y_inc = sign * 4.0f * (float)sin_deg(deg);
}
/*****************************************************************************
* Draw the ball.
*****************************************************************************/
void DrawBoingBall(DRAW_BALL_ENUM drawBallHow)
{
float dt_total, dt2;
GLenum error;
/* Reset error */
error = glGetError();
memcpy(modelview, modelview_orig, sizeof(modelview));
/* Another relative Z translation to separate objects. */
mat4x4_translate_in_place(modelview, 0.0f, 0.0f, DIST_BALL);
/* Update ball position and rotation (iterate if necessary) */
dt_total = dt;
while (dt_total > 0.0)
{
dt2 = dt_total > MAX_DELTA_T ? MAX_DELTA_T : dt_total;
dt_total -= dt2;
BounceBall(dt2);
deg_rot_y = TruncateDeg(deg_rot_y + deg_rot_y_inc * ((float)dt2 * ANIMATION_SPEED));
}
/* Set ball position */
mat4x4_translate_in_place(modelview, ball_x, ball_y, 0.0f);
/* Offset the shadow. */
if (drawBallHow == DRAW_BALL_SHADOW)
{
mat4x4_translate_in_place(modelview, SHADOW_OFFSET_X, SHADOW_OFFSET_Y, SHADOW_OFFSET_Z);
}
/* Tilt the ball. */
mat4x4_rotate(modelview, modelview, 0.0f, 0.0f, 1.0f, deg2rad(-20.0f));
/* Continually rotate ball around Y axis. */
mat4x4_rotate(modelview, modelview, 0.0f, 1.0f, 0.0f, deg2rad(deg_rot_y));
/* Set OpenGL state for Boing ball. */
glCullFace(GL_FRONT);
glEnable(GL_CULL_FACE);
mat4x4_mul(mvp, projection, modelview);
glUniformMatrix4fv(mvp_matrix_loc, 1, GL_FALSE, (GLfloat*)mvp);
if (drawBallHow == DRAW_BALL_SHADOW)
{
glUniform4fv(vertex_color_loc, 1, color_shadow);
}
else
{
glUniform4fv(vertex_color_loc, 1, color1);
}
glDrawArrays(GL_TRIANGLES, 0, facet_array_size / sizeof(vec3));
if (drawBallHow == DRAW_BALL_SHADOW)
{
glUniform4fv(vertex_color_loc, 1, color_shadow);
}
else
{
glUniform4fv(vertex_color_loc, 1, color2);
}
glDrawArrays(GL_TRIANGLES, facet_array_size / sizeof(vec3), facet_array_size / sizeof(vec3));
error = glGetError();
if (error != GL_NO_ERROR)
{
fprintf(stderr, "GL Error: 0x%04X in ball draw function\n", error);
}
return;
}
/*****************************************************************************
* Generate grid of lines
*****************************************************************************/
void GenerateGrid(void)
{
const int rowTotal = 12; /* must be divisible by 2 */
const int colTotal = rowTotal; /* must be same as rowTotal */
const float widthLine = 2.0f; /* should be divisible by 2 */
const float sizeCell = GRID_SIZE / rowTotal;
const float z_offset = -40.0f;
int row, col;
float xl, xr;
float yt, yb;
int grid_idx = 0;
/* "* 6" - 6 vertices per line (two triangles) */
grid_array_size = ((rowTotal + 1) + (colTotal + 1)) * 6 * sizeof(vec3);
grid_vertices = calloc(1, facet_array_size);
if (grid_vertices == NULL)
{
fprintf(stderr, "Can't allocate memory for grid vertices!\n");
glfwTerminate();
exit(EXIT_FAILURE);
}
/* Generate vertical lines (as skinny 3D rectangles). */
for (col = 0; col <= colTotal; col++)
{
/* Compute coords of line. */
xl = -GRID_SIZE / 2 + col * sizeCell;
xr = xl + widthLine;
yt = GRID_SIZE / 2;
yb = -GRID_SIZE / 2 - widthLine;
memcpy(grid_vertices[grid_idx + 0], (vec3){xr, yt, z_offset}, sizeof(vec3)); /* NE, V0 */
memcpy(grid_vertices[grid_idx + 1], (vec3){xl, yt, z_offset}, sizeof(vec3)); /* NW, V1 */
memcpy(grid_vertices[grid_idx + 2], (vec3){xl, yb, z_offset}, sizeof(vec3)); /* SW, V2 */
memcpy(grid_vertices[grid_idx + 3], (vec3){xr, yt, z_offset}, sizeof(vec3)); /* NE, V0 */
memcpy(grid_vertices[grid_idx + 4], (vec3){xl, yb, z_offset}, sizeof(vec3)); /* SW, V2 */
memcpy(grid_vertices[grid_idx + 5], (vec3){xr, yb, z_offset}, sizeof(vec3)); /* SE, V3 */
grid_idx += 6;
}
/* Generate horizontal lines (as skinny 3D rectangles). */
for (row = 0; row <= rowTotal; row++)
{
/* Compute coords of line. */
yt = GRID_SIZE / 2 - row * sizeCell;
yb = yt - widthLine;
xl = -GRID_SIZE / 2;
xr = GRID_SIZE / 2 + widthLine;
memcpy(grid_vertices[grid_idx + 0], (vec3){xr, yt, z_offset}, sizeof(vec3)); /* NE, V0 */
memcpy(grid_vertices[grid_idx + 1], (vec3){xl, yt, z_offset}, sizeof(vec3)); /* NW, V1 */
memcpy(grid_vertices[grid_idx + 2], (vec3){xl, yb, z_offset}, sizeof(vec3)); /* SW, V2 */
memcpy(grid_vertices[grid_idx + 3], (vec3){xr, yt, z_offset}, sizeof(vec3)); /* NE, V0 */
memcpy(grid_vertices[grid_idx + 4], (vec3){xl, yb, z_offset}, sizeof(vec3)); /* SW, V2 */
memcpy(grid_vertices[grid_idx + 5], (vec3){xr, yb, z_offset}, sizeof(vec3)); /* SE, V3 */
grid_idx += 6;
}
}
/*****************************************************************************
* Draw the purple grid of lines, behind the Boing ball.
* When the Workbench is dropped to the bottom, Boing shows 12 rows.
*****************************************************************************/
void DrawGrid(void)
{
memcpy(modelview, modelview_orig, sizeof(modelview));
glDisable(GL_CULL_FACE);
/* Another relative Z translation to separate objects. */
mat4x4_translate_in_place(modelview, 0.0f, 0.0f, DIST_BALL);
mat4x4_mul(mvp, projection, modelview);
glUniformMatrix4fv(mvp_matrix_loc, 1, GL_FALSE, (GLfloat*)mvp);
glUniform4fv(vertex_color_loc, 1, grid_color);
glDrawArrays(GL_TRIANGLES, (facet_array_size + facet_array_size) / sizeof(vec3),
(facet_array_size + facet_array_size) / sizeof(vec3));
return;
}
/*======================================================================*
* main()
*======================================================================*/
int main(void)
{
GLFWwindow* window;
/* Init GLFW */
if (!glfwInit())
exit(EXIT_FAILURE);
window = glfwCreateWindow(400, 400, "Boing OpenGL ES 2.x (classic Amiga demo)", NULL, NULL);
if (!window)
{
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwSetWindowAspectRatio(window, 1, 1);
glfwSetFramebufferSizeCallback(window, reshape);
glfwSetKeyCallback(window, key_callback);
glfwSetMouseButtonCallback(window, mouse_button_callback);
glfwSetCursorPosCallback(window, cursor_position_callback);
glfwMakeContextCurrent(window);
gladLoadGLES2(glfwGetProcAddress);
glfwSwapInterval(1);
glfwGetFramebufferSize(window, &width, &height);
reshape(window, width, height);
glfwSetTime(0.0);
init();
/* Main loop */
for (;;)
{
/* Timing */
t = glfwGetTime();
dt = t - t_old;
t_old = t;
/* Draw one frame */
display();
/* Swap buffers */
glfwSwapBuffers(window);
glfwPollEvents();
/* Check if we are still running */
if (glfwWindowShouldClose(window))
break;
}
glfwTerminate();
exit(EXIT_SUCCESS);
}