What is the simplest way of applying a normal map to a textured four vertex polygon in SDL? Do you have to create a shader or is there a simpler way? I have here my code that creates a textured rotating cube, with a rotating satellite light.
What additions to my code do I need to do if I want to use the generated texture (tex_Norm = generateTexture()) as a normal map also?
#include <windows.h>
#include <SDL.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <GL/glext.h>
#include <math.h>
void initAll();
void setupBox();
void mainloop();
unsigned int generateTexture();
void handle_inputs();
void updateScreen();
void clean_up();
int scrWidth, scrHeight, flags;
bool bQuit = false;
float angle = 0.0f;
GLuint tex_Box, tex_Norm;
struct sVert
{
float x;
float y;
float z;
};
class cPolygon
{
public:
int v[4];
void fillverts(int v1, int v2, int v3, int v4) {
v[0] = v1;
v[1] = v2;
v[2] = v3;
v[3] = v4;
}
} p[6];
sVert pv[8];
int main(int argc, char *argv[])
{
initAll();
mainloop();
clean_up();
return 0;
}
void initAll()
{
scrWidth = 800;
scrHeight = 600;
SDL_InitSubSystem(SDL_INIT_VIDEO);
SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 );
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
flags = SDL_OPENGL | SDL_ANYFORMAT ;
SDL_SetVideoMode(scrWidth, scrHeight, 16, flags);
glMatrixMode( GL_PROJECTION );
glLoadIdentity( );
gluPerspective( 45.0f, (GLfloat)scrWidth/(GLfloat)scrHeight, 1.0f, 500.0f );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity( );
glEnable (GL_DEPTH_TEST);
glEnable (GL_LIGHTING);
glEnable (GL_LIGHT0);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_ALPHA);
SDL_WM_SetCaption( "Normal Mapping", NULL );
tex_Box = generateTexture();
tex_Norm = generateTexture();
setupBox();
}
void setupBox()
{
for (int z=0;z<2;z++)
for (int y=0;y<2;y++)
for (int x=0;x<2;x++)
{
pv[x+y*2+z*4].x = -1.0+x;
pv[x+y*2+z*4].y = -1.0+y;
pv[x+y*2+z*4].z = -1.0+z;
}
// Box object
p[0].fillverts (0, 1, 3, 2); // above
p[1].fillverts (4, 5, 1, 0); // behind
p[2].fillverts (6, 7, 3, 2); // in front
p[3].fillverts (5, 7, 3, 1); // right
p[4].fillverts (0, 2, 6, 4); // left
p[5].fillverts (7, 6, 4, 5); // below
}
unsigned int generateTexture()
{
BYTE data[128*128*3];
unsigned int id;
for (int x=0;x<128;x++)
for (int y=0;y<128;y++)
{
data[y*128*3+x*3+0] = x; // Red
data[y*128*3+x*3+1] = y; // Green
data[y*128*3+x*3+2] = 128-(abs(64-x)+abs(64-y)); // Blue
}
glGenTextures(1, &id);
glBindTexture(GL_TEXTURE_2D, id);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 128, 128, 0, GL_RGB, GL_BYTE, data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
return id;
}
void mainloop()
{
while(bQuit == false)
{
handle_inputs();
updateScreen();
angle += 1.5f;
Sleep(50);
}
}
void handle_inputs()
{
SDL_PumpEvents();
Uint8 * keystate = SDL_GetKeyState(NULL);
if(keystate[SDLK_ESCAPE]) bQuit = true;
}
void updateScreen()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glPushMatrix();
glTranslatef(0.0f, 0.0f, -3.0f);
glRotatef(-angle*2.0, 1.0f, 1.0f, 1.0f);
// Setup a light source
float lpos[] = {0.0, 0.0, 2.0, 1.0}; // position
float ldif[] = {1.0, 1.0, 1.0, 1.0}; // diffuse
float lamb[] = {0.3, 0.3, 0.2, 1.0}; // ambient
glLightfv(GL_LIGHT0, GL_POSITION, lpos);
glLightfv(GL_LIGHT0, GL_DIFFUSE, ldif);
glLightfv(GL_LIGHT0, GL_AMBIENT, lamb);
glPopMatrix();
glPushMatrix();
glTranslatef(0.5f, 0.5f, -3.0f);
glRotatef(angle, 1.0f, 1.0f, 1.0f);
// Draw box object
glBindTexture(GL_TEXTURE_2D, tex_Box);
glEnable(GL_TEXTURE_2D);
glBegin(GL_QUADS);
for(int pi=0; pi<6; pi++)
for(int vi=0; vi<4; vi++)
{
switch(vi) {
case 0: glTexCoord2d(0.0,2.0); break;
case 1: glTexCoord2d(0.0,0.0); break;
case 2: glTexCoord2d(2.0,0.0); break;
case 3: glTexCoord2d(2.0,2.0); break; };
glVertex3f( pv[ p[pi].v[vi] ].x,
pv[ p[pi].v[vi] ].y,
pv[ p[pi].v[vi] ].z );
};
glEnd();
glDisable(GL_TEXTURE_2D);
glPopMatrix();
glFinish();
SDL_GL_SwapBuffers();
}
void clean_up()
{
SDL_QuitSubSystem(SDL_INIT_VIDEO);
glDeleteTextures(1, &tex_Box);
glDeleteTextures(1, &tex_Norm);
SDL_Quit();
}
Sorry, but if you want to use modern OpenGL features, you need modern OpenGL, which means shaders. :( That also means all your lighting needs to be done manually in the shader, so your program is going to get quite a bit more complicated, but that's the price you pay for cool images.
Explaining in detail how to do normal mapping wouldn't fit here, but there are very nice tutorials out there, for example http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-13-normal-mapping/.
Good luck!