glTexCoordPointer output not as expected [closed] - c++

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I am trying to use glDrawElements , glTexCoordPointer and glTexImage1D to create a 1D texture, render a surface dataset and color the vertices according to their height value.
GLuint tex = 0;
My texture generation:
glGenTextures( 1, &tex );
glBindTexture( GL_TEXTURE_1D, tex );
unsigned char pixels[] =
{
255, 0, 0, 255,
0, 255, 0, 255,
0, 0, 255, 255,
};
glTexImage1D( GL_TEXTURE_1D, 0, GL_RGBA, 3, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels );
glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL );
glTexParameteri( GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
glTexParameteri( GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
vArray is an array which stores the vertices for rendering.
float vArray[12] = {
0.0, 1.0, 0.0,
0.0, 3.0, 1.0,
1.0, 2.0, 0.0,
1.0, 1.0, 1.0,
}
iArray is an array which stores the indices for rendering.
int iSize = 6;
int iArray[6] = {
0, 2, 1,
2, 1, 4,
}
tArray is an array which stores the normalised heights.
GLfloat tArray[4] = {
0.0, 0.3, 1.0, 0.0,
}
My render code:
glEnable(GL_TEXTURE_1D);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glBindTexture(GL_TEXTURE_1D, tex);
glTexCoordPointer(1, GL_FLOAT, sizeof(GL_FLOAT), tArray);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3 ,GL_FLOAT,0, vArray);
glDrawElements(GL_TRIANGLES, iSize, GL_UNSIGNED_INT, iArray);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisable(GL_TEXTURE_1D);
The final output is not as I expected, hoping somebody can point out my mistakes.

Answer 1

RE: your glTexCoordPointer() call: Tightly-packed arrays usually use 0 for stride.
vArray and tArray only have four elements, not five, so the 4 in iArray will cause OpenGL to read off the ends of those arrays into garbage (if you're lucky) or segfaults (if you're not).
All together:
#include <GL/glew.h>
#include <GL/glut.h>
GLuint tex = 0;
void display()
{
glClear( GL_COLOR_BUFFER_BIT );
float vArray[] =
{
-0.5, -0.5,
0.5, -0.5,
0.5, 0.5,
-0.5, 0.5,
};
GLfloat tArray[] =
{
0.0, 0.3, 1.0, 0.0,
};
unsigned int iArray[] =
{
0, 1, 2,
2, 3, 0,
};
glEnable( GL_TEXTURE_1D );
glBindTexture( GL_TEXTURE_1D, tex );
glEnableClientState( GL_TEXTURE_COORD_ARRAY );
glTexCoordPointer( 1, GL_FLOAT, 0, tArray );
glEnableClientState( GL_VERTEX_ARRAY );
glVertexPointer( 2, GL_FLOAT, 0, vArray );
glDrawElements( GL_TRIANGLES, 6, GL_UNSIGNED_INT, iArray );
glDisableClientState( GL_TEXTURE_COORD_ARRAY );
glDisableClientState( GL_VERTEX_ARRAY );
glDisable( GL_TEXTURE_1D );
glutSwapBuffers();
}
int main( int argc, char** argv )
{
glutInit( &argc, argv );
glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE );
glutInitWindowSize( 400, 400 );
glutCreateWindow( "GLUT" );
glewInit();
glGenTextures( 1, &tex );
glBindTexture( GL_TEXTURE_1D, tex );
unsigned char pixels[] =
{
255, 0, 0, 255,
0, 255, 0, 255,
0, 0, 255, 255,
};
glTexImage1D( GL_TEXTURE_1D, 0, GL_RGBA, 3, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels );
glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL );
glTexParameteri( GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
glTexParameteri( GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glutDisplayFunc( display );
glutMainLoop();
return 0;
}
EDIT: 2D version:
#include <GL/glew.h>
#include <GL/glut.h>
GLuint tex = 0;
void display()
{
glClear( GL_COLOR_BUFFER_BIT );
float vArray[] =
{
-0.5, -0.5,
0.5, -0.5,
0.5, 0.5,
-0.5, 0.5,
};
GLfloat tArray[] =
{
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
};
unsigned int iArray[] =
{
0, 1, 2,
2, 3, 0,
};
glEnable( GL_TEXTURE_2D );
glBindTexture( GL_TEXTURE_2D, tex );
glEnableClientState( GL_TEXTURE_COORD_ARRAY );
glTexCoordPointer( 2, GL_FLOAT, 0, tArray );
glEnableClientState( GL_VERTEX_ARRAY );
glVertexPointer( 2, GL_FLOAT, 0, vArray );
glDrawElements( GL_TRIANGLES, 6, GL_UNSIGNED_INT, iArray );
glDisableClientState( GL_TEXTURE_COORD_ARRAY );
glDisableClientState( GL_VERTEX_ARRAY );
glDisable( GL_TEXTURE_2D );
glutSwapBuffers();
}
int main( int argc, char** argv )
{
glutInit( &argc, argv );
glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE );
glutInitWindowSize( 400, 400 );
glutCreateWindow( "GLUT" );
glewInit();
glGenTextures( 1, &tex );
glBindTexture( GL_TEXTURE_2D, tex );
unsigned char pixels[] =
{
255, 0, 0, 255,
0, 255, 0, 255,
0, 0, 255, 255,
0, 0, 255, 255,
};
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels );
glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glutDisplayFunc( display );
glutMainLoop();
return 0;
}