[Plib-users] Drawing a simple triangle

[Peter P. <pet...@st...>]

I have tried the program below, but it only shows a black screen. Can
anybody explain why? The program works if I make direct gl-calls (just
comment out the first line).

---- ssg_triangle.cc ---

#define USE_SSG 1

#include <GL/gl.h>
#include <GL/glu.h>

#include <plib/ssg.h>
#include <SDL/SDL.h>
#include <iostream>

using namespace std;

ssgRoot* _root;
#define SCREEN_WIDTH 320
#define SCREEN_HEIGHT 240
#define SCREEN_BPP 24

void init()
{
	int videoFlags;
	SDL_Surface* surface;
	const SDL_VideoInfo *videoInfo;

	if ( SDL_Init( SDL_INIT_VIDEO ) < 0 ) {
		fprintf( stderr, "Video initialization failed: %s\n",  SDL_GetError( ) );
		exit(0);
	}

	videoFlags  = SDL_OPENGL;
	videoFlags |= SDL_GL_DOUBLEBUFFER;
	videoFlags |= SDL_HWPALETTE;      
	videoFlags |= SDL_HWSURFACE;
	surface = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, videoFlags );

	if ( !surface ) {
		fprintf( stderr,  "Video mode set failed: %s\n", SDL_GetError( ) );
		exit(0);
	}

#ifdef USE_SSG
	ssgInit();
	
	glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f ) ;
	glEnable ( GL_DEPTH_TEST ) ;
	ssgVertexArray* vertices = new ssgVertexArray;
	sgVec3 x = { 0.5f, -0.25f, 0.0f };
	sgVec3 y = { -0.5f, -0.25f, 0.0f };
	sgVec3 z = { 0.0f, 0.75f, 0.0f };
	vertices->add(x);
	vertices->add(y);
	vertices->add(z);

	sgVec4 white = { 1.0f, 1.0f, 1.0f, 0.5f };
	ssgColourArray* colours = new ssgColourArray;
	colours->add(white);
	colours->add(white);
	colours->add(white);
	ssgNormalArray* normals = new ssgNormalArray(3);
	sgVec3 normal = { 0, 0, 1 };
	normals->add(normal);
	normals->add(normal);
	normals->add(normal);
	ssgTexCoordArray* texs = new ssgTexCoordArray(3);
	sgVec2 tex_vec = {0,0};
	texs->add(tex_vec);
	texs->add(tex_vec);
	texs->add(tex_vec);
	
	ssgVtxTable* n = new ssgVtxTable(GL_TRIANGLES, vertices, normals, texs, colours);
	ssgTransform* trans = new ssgTransform;
	trans->addKid(n);

	_root = new ssgRoot;
	_root->addKid(trans);
#endif
}

void update()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) ;

#ifdef USE_SSG
	ssgCullAndDraw(_root);

#else
	glLoadIdentity();
	
	glColor3f(1.0f, 1.0f, 1.0f);
	glBegin(GL_TRIANGLES);
	glVertex2f(0.5f, -0.25f);
	glVertex2f(-0.5f, -0.25f);
	glVertex2f(0.0f, 0.75f);
	glEnd();
#endif
	SDL_GL_SwapBuffers( );
}

int main(int argc, char *argv[])
{
	init();
	for(unsigned int i = 0; i < 1000; i++) {
		update();
	}
	return 0;
}

-- 
Yours 
Peter Poulsen