Jeff Molofee - NeHe's OpenGL Tutorials

glDisable(GL_BLEND);

glDisable(GL_LIGHTING);

doCube();

• Use inverted bump-texture

• Enable Blending GL_ONE, GL_ONE

• Keep Lighting disabled

• Use offset texture-coordinates (This means that you call SetUpBumps() before each face of the cube

• Do the geometry

This will render a cube with the correct emboss bump mapping, but without colors.

You could save computing time by just rotating the lightvector into inverted direction. However, this didn't work out correctly, so we do it the plain way: rotate each normal and center-point the same way we rotate our geometry!

glBindTexture(GL_TEXTURE_2D, invbump[filter]);

glBlendFunc(GL_ONE,GL_ONE);

glDepthFunc(GL_LEQUAL);

glEnable(GL_BLEND);

glBegin(GL_QUADS);

// Front Face

n[0]=0.0f;

n[1]=0.0f;

n[2]=1.0f;

s[0]=1.0f;

s[1]=0.0f;

s[2]=0.0f;

t[0]=0.0f;

t[1]=1.0f;

t[2]=0.0f;

for (i=0; i<4; i++) {

c[0]=data[5*i+2];

c[1]=data[5*i+3];

c[2]=data[5*i+4];

SetUpBumps(n,c,l,s,t);

glTexCoord2f(data[5*i]+c[0], data[5*i+1]+c[1]);

glVertex3f(data[5*i+2], data[5*i+3], data[5*i+4]);

}

// Back Face

n[0]=0.0f;

n[1]=0.0f;

n[2]=-1.0f;

s[0]=-1.0f;

s[1]=0.0f;

s[2]=0.0f;

t[0]=0.0f;

t[1]=1.0f;

t[2]=0.0f;

for (i=4; i<8; i++) {

c[0]=data[5*i+2];

c[1]=data[5*i+3];

c[2]=data[5*i+4];

SetUpBumps(n,c,l,s,t);

glTexCoord2f(data[5*i]+c[0], data[5*i+1]+c[1]);

glVertex3f(data[5*i+2], data[5*i+3], data[5*i+4]);

}

// Top Face

n[0]=0.0f;

n[1]=1.0f;

n[2]=0.0f;

s[0]=1.0f;

s[1]=0.0f;

s[2]=0.0f;

t[0]=0.0f;

t[1]=0.0f;

t[2]=-1.0f;

for (i=8; i<12; i++) {

c[0]=data[5*i+2];

c[1]=data[5*i+3];

c[2]=data[5*i+4];

SetUpBumps(n,c,l,s,t);

glTexCoord2f(data[5*i]+c[0], data[5*i+1]+c[1]);

glVertex3f(data[5*i+2], data[5*i+3], data[5*i+4]);

}

// Bottom Face

n[0]=0.0f;

n[1]=-1.0f;

n[2]=0.0f;

s[0]=-1.0f;

s[1]=0.0f;

s[2]=0.0f;

t[0]=0.0f;

t[1]=0.0f;

t[2]=-1.0f;

for (i=12; i<16; i++) {

c[0]=data[5*i+2];

c[1]=data[5*i+3];

c[2]=data[5*i+4];

SetUpBumps(n,c,l,s,t);

glTexCoord2f(data[5*i]+c[0], data[5*i+1]+c[1]);

glVertex3f(data[5*i+2], data[5*i+3], data[5*i+4]);

}

// Right Face

n[0]=1.0f;

n[1]=0.0f;

n[2]=0.0f;

s[0]=0.0f;

s[1]=0.0f;

s[2]=-1.0f;

t[0]=0.0f;

t[1]=1.0f;

t[2]=0.0f;

for (i=16; i<20; i++) {

c[0]=data[5*i+2];

c[1]=data[5*i+3];

c[2]=data[5*i+4];

SetUpBumps(n,c,l,s,t);

glTexCoord2f(data[5*i]+c[0], data[5*i+1]+c[1]);

glVertex3f(data[5*i+2], data[5*i+3], data[5*i+4]);

}

// Left Face

n[0]=-1.0f;

n[1]=0.0f;

n[2]=0.0f;

s[0]=0.0f;

s[1]=0.0f;

s[2]=1.0f;

t[0]=0.0f;

t[1]=1.0f;

t[2]=0.0f;

for (i=20; i<24; i++) {

c[0]=data[5*i+2];

c[1]=data[5*i+3];

c[2]=data[5*i+4];

SetUpBumps(n,c,l,s,t);

glTexCoord2f(data[5*i]+c[0], data[5*i+1]+c[1]);

glVertex3f(data[5*i+2], data[5*i+3], data[5*i+4]);

}

glEnd();

• Use (colored) base-texture

• Enable Blending GL_DST_COLOR, GL_SRC_COLOR

• This blending equation multiplies by 2: (Cdst*Csrc)+(Csrc*Cdst)=2(Csrc*Cdst)!

• Enable Lighting to do the ambient and diffuse stuff

• Reset GL_TEXTURE-matrix to go back to "normal" texture coordinates

• Do the geometry

This will finish cube-rendering, complete with lighting. Since we can switch back and forth between multitexturing and non-multitexturing, we have to reset the texture-environment to "normal" GL_MODULATE first. We only do the third pass, if the user doesn't want to see just the emboss.

if (!emboss) {

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

glBindTexture(GL_TEXTURE_2D,texture[filter]);

glBlendFunc(GL_DST_COLOR,GL_SRC_COLOR);

glEnable(GL_LIGHTING);

doCube();

}

• update geometry (esp. rotations)

• do the Logos

xrot+=xspeed;

yrot+=yspeed;

if (xrot>360.0f) xrot-=360.0f;

if (xrot<0.0f) xrot+=360.0f;

if (yrot>360.0f) yrot-=360.0f;

if (yrot<0.0f) yrot+=360.0f;

/* LAST PASS: Do The Logos! */

doLogo();

return true; // Keep Going

}

This function will do the whole mess in 2 passes with multitexturing support. We support two texel-units. More would be extreme complicated due to the blending equations. Better trim to TNT instead. Note that almost the only difference to doMesh1TexelUnits() is, that we send two sets of texture-coordinates for each vertex!

bool doMesh2TexelUnits(void) {

GLfloat c[4]={0.0f,0.0f,0.0f,1.0f}; // Holds Current Vertex

GLfloat n[4]={0.0f,0.0f,0.0f,1.0f}; // Normalized Normal Of Current Surface

GLfloat s[4]={0.0f,0.0f,0.0f,1.0f}; // s-Texture Coordinate Direction, Normalized

GLfloat t[4]={0.0f,0.0f,0.0f,1.0f}; // t-Texture Coordinate Direction, Normalized

GLfloat l[4]; // Holds Our Lightposition To Be Transformed Into Object Space

GLfloat Minv[16]; // Holds The Inverted Modelview Matrix To Do So

int i;

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer

// Build Inverse Modelview Matrix First. This Substitutes One Push/Pop With One glLoadIdentity();

// Simply Build It By Doing All Transformations Negated And In Reverse Order

glLoadIdentity();

glRotatef(-yrot,0.0f,1.0f,0.0f);

glRotatef(-xrot,1.0f,0.0f,0.0f);

glTranslatef(0.0f,0.0f,-z);

glGetFloatv(GL_MODELVIEW_MATRIX,Minv);

glLoadIdentity();