Jump to content
  • Advertisement
Sign in to follow this  
neverland

a problem about glBlendEquation function

This topic is 4695 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hello All I am reading "The Red Book" 4th edition. In chapter 6 the book introduces a blend function called glBlendEquation. I wrote a program using it. The code was successfully compiled, but an error occured when I ran it. code:
#include <Windows.h>
#include <gl/glew.h>
#include <gl/glut.h>

void init()
{
	glClearColor(1.0, 1.0, 0.0, 0.0);
	glBlendFunc(GL_ONE, GL_ONE);
	glEnable(GL_BLEND);
}

void display()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(0.0, 0.0, 1.0);
	glBlendEquation(GL_FUNC_ADD); // this line causes a run-time error!
	glRectf(-0.5, -0.5, 0.5, 0.5);
	glFlush();
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowPosition(200, 100);
	glutInitWindowSize(400, 400);
	glutCreateWindow("Blend Equation");

	init();
	glutDisplayFunc(display);
	glutMainLoop();
}
anything wrong?

Share this post


Link to post
Share on other sites
Advertisement
glBlendEquation () is not part of the core OpenGL functions. You should check for GL_ARB_imaging extension before using it. I guess your hardware doesn't support that extension.

Share this post


Link to post
Share on other sites
Quote:
Original post by Skeleton_V@T
glBlendEquation () is not part of the core OpenGL functions. You should check for GL_ARB_imaging extension before using it. I guess your hardware doesn't support that extension.


My graphics card is Geforce FX5700 which dose support GL_ARB_imaging extension.
And I've updated OpenGL driver to 2.0.

Any other reason?

Share this post


Link to post
Share on other sites
ive never used glew but i think u need to call a function before u can use it to setup the extension points (ie just including the header aint enuf) eg
init_glew();

glBlendEquation is part of gl1.2 i think + gffx supports it in hardware
also GL_FUNC_ADD is just normal blending use GL_LOGIC_OP for some different blending methods ( coincidently i was playing around with today)

Share this post


Link to post
Share on other sites
Quote:
Original post by zedzeek
ive never used glew but i think u need to call a function before u can use it to setup the extension points (ie just including the header aint enuf) eg
init_glew();

glBlendEquation is part of gl1.2 i think + gffx supports it in hardware
also GL_FUNC_ADD is just normal blending use GL_LOGIC_OP for some different blending methods ( coincidently i was playing around with today)


I couldn't find glBlendEquation ni gl.h, so I googled.
And I found the GLEW library which includes glBlendEquation, but I don't know how to use it.
If I don't use GLEW library, is there any other method could let me use the extensions in OpenGL 1.2 or later?

Share this post


Link to post
Share on other sites
You may try OpenGL Easy Extension (a.k.a GLee) library. Before using any OpenGL extensions, you check for it's availability roughly like this:
if (GLEE_ARB_multitexture)    //is multitexture support available?
{
glMultiTexCoord2fARB(...); //safe to use multitexture
}


To use GLee in your project, you need to include GLee.h, put it's header and library files into default Include and Lib directories, and that's all.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!