I am new to OpenGL and am learning it for the purpose of some simulation that I am doing as part of my research work. I have been following the tutorials given at http://openglbook.com/chapter-2-vertices-and-shapes.html and am using the code which draws a triangle. I am trying to add some code to it so that I can rotate the triangle using mouse upon display. I am using glTranslatef and glRotatef to achieve this. I understand that glrotate takes 4 arguments first being the angle of rotation, the last three form the vector centred at origin around which rotation is intended. I am printing captured values from my motion func and the mouse input is being captured. But my triangle is not rotating. Any help will be much appreciated. Thanks! Code below.
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <GL/glew.h>
#include <GL/freeglut.h>
#define WINDOW_TITLE_PREFIX "Chapter 2"
int
CurrentWidth = 800,
CurrentHeight = 800,
WindowHandle = 0;
unsigned FrameCount = 0;
GLuint
VertexShaderId,
FragmentShaderId,
ProgramId,
VaoId,
VboId,
ColorBufferId;
// mouse controls
int mouse_old_x, mouse_old_y;
int mouse_buttons = 0;
float rotate_x = 0.0, rotate_y = 0.0;
float translate_z = -3.0;
const GLchar* VertexShader =
{
"#version 400\n"\
"layout(location=0) in vec4 in_Position;\n"\
"layout(location=1) in vec4 in_Color;\n"\
"out vec4 ex_Color;\n"\
"void main(void)\n"\
"{\n"\
" gl_Position = in_Position;\n"\
" ex_Color = in_Color;\n"\
"}\n"
};
const GLchar* FragmentShader =
{
"#version 400\n"\
"in vec4 ex_Color;\n"\
"out vec4 out_Color;\n"\
"void main(void)\n"\
"{\n"\
" out_Color = ex_Color;\n"\
"}\n"
};
void Initialize(int, char*[]);
void InitWindow(int, char*[]);
void ResizeFunction(int, int);
void RenderFunction(void);
void TimerFunction(int);
void IdleFunction(void);
void Cleanup(void);
void CreateVBO(void);
void DestroyVBO(void);
void CreateShaders(void);
void DestroyShaders(void);
//Mouse Movements//
void mouse(int button, int state, int x, int y);
void motion(int x, int y);
int main(int argc, char* argv[])
{
Initialize(argc, argv);
glutMainLoop();
exit(EXIT_SUCCESS);
}
void Initialize(int argc, char* argv[])
{
GLenum GlewInitResult;
InitWindow(argc, argv);
glewExperimental = GL_TRUE;
GlewInitResult = glewInit();
if (GLEW_OK != GlewInitResult) {
fprintf(
stderr,
"ERROR: %s\n",
glewGetErrorString(GlewInitResult)
);
exit(EXIT_FAILURE);
}
fprintf(
stdout,
"INFO: OpenGL Version: %s\n",
glGetString(GL_VERSION)
);
CreateShaders();
CreateVBO();
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
}
void InitWindow(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitContextVersion(4, 0);
glutInitContextFlags(GLUT_FORWARD_COMPATIBLE);
glutInitContextProfile(GLUT_CORE_PROFILE);
glutSetOption(
GLUT_ACTION_ON_WINDOW_CLOSE,
GLUT_ACTION_GLUTMAINLOOP_RETURNS
);
glutInitWindowSize(CurrentWidth, CurrentHeight);
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
WindowHandle = glutCreateWindow(WINDOW_TITLE_PREFIX);
if(WindowHandle < 1) {
fprintf(
stderr,
"ERROR: Could not create a new rendering window.\n"
);
exit(EXIT_FAILURE);
}
glutReshapeFunc(ResizeFunction);
glutDisplayFunc(RenderFunction);
glutMouseFunc(mouse);
glutMotionFunc(motion);
glutIdleFunc(IdleFunction);
glutTimerFunc(0, TimerFunction, 0);
glutCloseFunc(Cleanup);
}
void ResizeFunction(int Width, int Height)
{
CurrentWidth = Width;
CurrentHeight = Height;
glViewport(0, 0, CurrentWidth, CurrentHeight);
}
void RenderFunction(void)
{
++FrameCount;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// set view matrix
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, translate_z);
printf ("translate_x = %f rotate_x = %f rotate_y = %f \n",rotate_x,rotate_y,translate_z);
glRotatef(rotate_x, 1.0, 0.0, 0.0);
glRotatef(rotate_y, 0.0, 1.0, 0.0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glutSwapBuffers();
}
void IdleFunction(void)
{
glutPostRedisplay();
}
void TimerFunction(int Value)
{
if (0 != Value) {
char* TempString = (char*)
malloc(512 + strlen(WINDOW_TITLE_PREFIX));
sprintf(
TempString,
"%s: %d Frames Per Second @ %d x %d",
WINDOW_TITLE_PREFIX,
FrameCount * 4,
CurrentWidth,
CurrentHeight
);
glutSetWindowTitle(TempString);
free(TempString);
}
FrameCount = 0;
glutTimerFunc(250, TimerFunction, 1);
}
void Cleanup(void)
{
DestroyShaders();
DestroyVBO();
}
void CreateVBO(void)
{
GLfloat Vertices[] = {
-0.8f, -0.8f, 0.0f, 1.0f,
0.0f, 0.8f, 0.0f, 1.0f,
0.8f, -0.8f, 0.0f, 1.0f
};
GLfloat Colors[] = {
1.0f, 0.0f, 0.0f, 1.0f,
0.0f, 1.0f, 0.0f, 1.0f,
0.0f, 0.0f, 1.0f, 1.0f
};
GLenum ErrorCheckValue = glGetError();
glGenVertexArrays(1, &VaoId);
glBindVertexArray(VaoId);
glGenBuffers(1, &VboId);
glBindBuffer(GL_ARRAY_BUFFER, VboId);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(0);
glGenBuffers(1, &ColorBufferId);
glBindBuffer(GL_ARRAY_BUFFER, ColorBufferId);
glBufferData(GL_ARRAY_BUFFER, sizeof(Colors), Colors, GL_STATIC_DRAW);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(1);
ErrorCheckValue = glGetError();
if (ErrorCheckValue != GL_NO_ERROR)
{
fprintf(
stderr,
"ERROR: Could not create a VBO: %s \n",
gluErrorString(ErrorCheckValue)
);
exit(-1);
}
}
void DestroyVBO(void)
{
GLenum ErrorCheckValue = glGetError();
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glDeleteBuffers(1, &ColorBufferId);
glDeleteBuffers(1, &VboId);
glBindVertexArray(0);
glDeleteVertexArrays(1, &VaoId);
ErrorCheckValue = glGetError();
if (ErrorCheckValue != GL_NO_ERROR)
{
fprintf(
stderr,
"ERROR: Could not destroy the VBO: %s \n",
gluErrorString(ErrorCheckValue)
);
exit(-1);
}
}
void CreateShaders(void)
{
GLenum ErrorCheckValue = glGetError();
VertexShaderId = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(VertexShaderId, 1, &VertexShader, NULL);
glCompileShader(VertexShaderId);
FragmentShaderId = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(FragmentShaderId, 1, &FragmentShader, NULL);
glCompileShader(FragmentShaderId);
ProgramId = glCreateProgram();
glAttachShader(ProgramId, VertexShaderId);
glAttachShader(ProgramId, FragmentShaderId);
glLinkProgram(ProgramId);
glUseProgram(ProgramId);
ErrorCheckValue = glGetError();
if (ErrorCheckValue != GL_NO_ERROR)
{
fprintf(
stderr,
"ERROR: Could not create the shaders: %s \n",
gluErrorString(ErrorCheckValue)
);
exit(-1);
}
}
void DestroyShaders(void)
{
GLenum ErrorCheckValue = glGetError();
glUseProgram(0);
glDetachShader(ProgramId, VertexShaderId);
glDetachShader(ProgramId, FragmentShaderId);
glDeleteShader(FragmentShaderId);
glDeleteShader(VertexShaderId);
glDeleteProgram(ProgramId);
ErrorCheckValue = glGetError();
if (ErrorCheckValue != GL_NO_ERROR)
{
fprintf(
stderr,
"ERROR: Could not destroy the shaders: %s \n",
gluErrorString(ErrorCheckValue)
);
exit(-1);
}
}
////////////////////////////////////////////////////////////////////////////////
//! Keyboard events handler
////////////////////////////////////////////////////////////////////////////////
void KeyboardFunction(unsigned char key, int X, int Y)
{
switch (key)
{
case (27) :
exit(EXIT_SUCCESS);
break;
}
}
////////////////////////////////////////////////////////////////////////////////
//! Mouse event handlers
////////////////////////////////////////////////////////////////////////////////
void mouse(int button, int state, int x, int y)
{
if (state == GLUT_DOWN)
{
mouse_buttons |= 1<<button;
printf("Mouse Button was pressed \n");
}
else if (state == GLUT_UP)
{
mouse_buttons = 0;
}
mouse_old_x = x;
mouse_old_y = y;
}
void motion(int x, int y)
{
float dx, dy;
dx = (float)(x - mouse_old_x);
dy = (float)(y - mouse_old_y);
if (mouse_buttons & 1)
{
rotate_x += dy * 0.2f;
rotate_y += dx * 0.2f;printf("ROTATE value is being set \n");
}
else if (mouse_buttons & 4)
{
translate_z += dy * 0.01f;printf("TRANSLATE is being set \n");
}
mouse_old_x = x;
mouse_old_y = y;
}
RenderFunction
where you are attempting to rotate: perhaps include additional description of that. \$\endgroup\$