paint each side of a cube with dif. color?

**arthurprs** · 28-04-2008, 08:10 PM

"im using opengl"

hi guys, im very noob on 3d, but i have good know how with opengl 2d (this helped), i already achieved how to draw the cubes and basic control of camera.

but in some cubes i have to colorize 1 side (or 2 or 3) with a dif color,
like http://upload.wikimedia.org/wikipedi...onal_prism.png

and i'm also wondering if i can make the cube bords with another dif color to make it more visible :?

thanks,
Arthur.

**Brainer** · 28-04-2008, 08:25 PM

I use this code to render a cube. You can call "glColor3f" after each face to render it in a different color.
[pascal]
procedure TCube.DoRender;
begin
glBegin(GL_QUADS);
// Top Face
glNormal3f(0.0, 1.0, 0.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 0.0);
glVertex3f(1.0, 1.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 1.0);
glVertex3f(1.0, 1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 1.0);
glVertex3f(-1.0, 1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 0.0);
glVertex3f(-1.0, 1.0, 1.0);

// Front Face
glNormal3f(0.0, 0.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 1.0);
glVertex3f(1.0, 1.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 1.0);
glVertex3f(-1.0, 1.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 0.0);
glVertex3f(-1.0, -1.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 0.0);
glVertex3f(1.0, -1.0, 1.0);

// Right Face
glNormal3f(1.0, 0.0, 0.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 1.0);
glVertex3f(1.0, 1.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 0.0);
glVertex3f(1.0, -1.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 0.0);
glVertex3f(1.0, -1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 1.0);
glVertex3f(1.0, 1.0, -1.0);

// Left Face
glNormal3f(-1.0, 0.0, 0.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 1.0);
glVertex3f(-1.0, 1.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 1.0);
glVertex3f(-1.0, 1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 0.0);
glVertex3f(-1.0, -1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 0.0);
glVertex3f(-1.0, -1.0, 1.0);

// Bottom Face
glNormal3f(0.0, -1.0, 0.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 0.0);
glVertex3f(-1.0, -1.0, 1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 1.0);
glVertex3f(-1.0, -1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 1.0);
glVertex3f(1.0, -1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 0.0);
glVertex3f(1.0, -1.0, 1.0);

// Back Face
glNormal3f(0.0, 0.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 0.0);
glVertex3f(1.0, -1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 0.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 0.0);
glVertex3f(-1.0, -1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0, 1.0);
glVertex3f(-1.0, 1.0, -1.0);

glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0, 1.0);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0, 1.0);
glVertex3f(1.0, 1.0, -1.0);

glEnd();
end;
[/pascal]

**arthurprs** · 28-04-2008, 08:40 PM

thanks, it solves the problem with the colored faces, but what about colored borders?

**Brainer** · 28-04-2008, 09:38 PM

The only idea that comes to my mind is to render the same cube twice, but the first one should be rendered with GL_LINES and the second one with GL_QUADS. I don't know if it's the best solution.

**User137** · 28-04-2008, 10:03 PM

The kind of borders you had there in the sample screenshot looks like having 2000 faces used or so in borders to get such a smooth details. That kind is achievable by making it with a modelling program and loading it up in your program, or making the borders with your own function. Consists of 12 cylinder shapes and 8 spheres.

Yeah other way is to render with GL_LINES after (or before, looks different with z-buffer) GL_QUADS and glLineWidth to set line width.

**arthurprs** · 28-04-2008, 10:41 PM

Originally Posted by User137

The kind of borders you had there in the sample screenshot looks like having 2000 faces used or so in borders to get such a smooth details. That kind is achievable by making it with a modelling program and loading it up in your program, or making the borders with your own function. Consists of 12 cylinder shapes and 8 spheres.

Yeah other way is to render with GL_LINES after (or before, looks different with z-buffer) GL_QUADS and glLineWidth to set line width.

it don't need to look like the sample, it only need to give a better contrast to the edges

edit: i will try render the same cube twice with GL_Lines on the second draw, i will post results soon

**arthurprs** · 30-04-2008, 08:36 PM

sorry for the delay...

everything is great, gl_lines worked great on the edges

but im having bad problems drawing the cubes it the way i need onto the screen =X

i need to draw a cube with some small cubes, and them remove the faces away, but...

i actually don't know how to position things with gltranslatef on the 3d scene =X

any link that explains that?

**User137** · 01-05-2008, 07:44 AM

Assume you would have function that renders small cube, wether it was with glBegin-glEnd or not, and task to render a 10x10 plane filled with cubes.

[pascal]var x,y: integer;
begin
for y:=0 to 9 do begin
glPushMatrix; // save current modelview matrix to stack
glTranslatef(0,y,0); // go to row start
for x:=0 to 9 do begin
RenderCube;
glTranslatef(1,0,0); // move 1 step on x-axis
end;
glPopMatrix; // load modelview matrix
end;
end;
[/pascal]

**arthurprs** · 01-05-2008, 04:11 PM

look what i have, any ideia why i need to move 2 insted of 1 as you say ?
(if i move 1 it does not position the cube above the another, they intersect)

[pascal] glLoadIdentity;
glTranslatef(-1,1,-20);

for m := 0 to l - 1 do
begin
for n := 0 to h - 1 do
begin
for i := 0 to w - 1 do
begin
test.Draw; //# a TCUBE.draw();
glTranslatef(2,0,0);
end;
glTranslatef(-2*w,2,0);
end;
glTranslatef(0,-2*h,-2);
end;

glTranslatef(6,-6,-10);

for m := 0 to l - 1 do
begin
for n := 0 to h - 1 do
begin
for i := 0 to w - 1 do
begin
test.Draw; //# a TCUBE.draw();
glTranslatef(2,0,0);
end;
glTranslatef(-2*w,2,0);
end;
glTranslatef(0,-2*h,-2);
end;[/pascal]

ps: in this code i rneder 2 cubes

**User137** · 01-05-2008, 07:24 PM

Originally Posted by arthurprs

look what i have, any ideia why i need to move 2 insted of 1 as you say ?
(if i move 1 it does not position the cube above the another, they intersect)

That would be, if your cube is min-maxed from -1 to 1. But I always render things from -0.5 to 0.5 or 0 to 1 (use -0.5 to 0.5 if you want to easily rotate around center point). That way you have simpler math when using grid or tile based game.

Your code works i guess, but don't forget to learn glPushMatrix and glPopMatrix. They are very useful, and in theory even faster than glTranslatef because there is no matrix multiplication, only simple memory copy.