Is this the correct way to do textures?

OpenGL Development
#1

Okay so let me start off by saying that this code does work. It does exactly what I expected it to do, no problem (whew!) My question is, is this the proper way? I know I shouldn’t be using a static context here, but this is my first foray into textures so I wanted the entire program to be in one simple class. I am more interested in things like, am I putting “glUseProgram()” in the proper place. I know, I know, if it works who cares, but I will eventually want to divide a lot of this into objects and I don’t want to put code places where it shouldn’t go.

Here is the code:

import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL12.*;
import static org.lwjgl.opengl.GL13.*;
import static org.lwjgl.opengl.GL15.*;
import static org.lwjgl.opengl.GL20.*;
import static org.lwjgl.opengl.GL30.*;
import static org.lwjgl.opengl.GL33.*;

import java.nio.ByteBuffer;
import java.nio.FloatBuffer;

import org.lwjgl.BufferUtils;
import org.lwjgl.LWJGLException;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;

public class TextureTestWindow {
	
	private static final float[] verts = {
		0.8f, 0.8f, 0f, 1f,
		-0.8f, 0.8f, 0f, 1f,
		-0.8f, -0.8f, 0f, 1f,	
		0.8f, -0.8f, 0f, 1f,
		};
	
	private static final float[] texCords = {
		1f, 0f, 
		0f, 0f, 
		0f, 1f, 
		1f, 1f};
	
	private static final byte[] texData = {
		(byte) 255, (byte) 0, (byte) 0, (byte) 255,
		(byte) 0, (byte) 255, (byte) 0, (byte) 255,
		(byte) 255, (byte) 255, (byte) 0, (byte) 255,
		(byte) 0, (byte) 0, (byte) 255, (byte) 255};
	
	private static final String easyTexVert = 
			"#version 330\n" +
			"layout (location = 0) in vec4 position;\n" + 
			"layout (location = 1) in vec2 texCord;\n" + 								
			"varying vec2 outTexCord;\n" + 									
			"void main() {\n" + 
			"	gl_Position = position;\n" +
			"	outTexCord = texCord;\n" +
			"}";
	
	private static final String easyTexFrag = 
			"#version 330\n" +
			"varying vec2 outTexCord;\n" +
			"out vec4 outputColor;\n" +							
			"uniform sampler2D tex;\n" + 					
			"void main() {\n" +
			"    outputColor = texture(tex, outTexCord);\n" +
			"}";

	public static void main(String[] args) {
		try {
			Display.setDisplayMode(new DisplayMode(500, 500));
			Display.create();
		} catch (LWJGLException e) {
			e.printStackTrace();
			System.exit(1);
		}
		
		// Create the program		

		int vShader = glCreateShader(GL_VERTEX_SHADER);
		glShaderSource(vShader, easyTexVert);
		glCompileShader(vShader);
		int fShader = glCreateShader(GL_FRAGMENT_SHADER);
		glShaderSource(fShader, easyTexFrag);
		glCompileShader(fShader);
		
		int program = glCreateProgram();
		glAttachShader(program, vShader);
		glAttachShader(program, fShader);
		glLinkProgram(program);
		glValidateProgram(program);

		// Set up the buffers
		
		FloatBuffer vertBuffer = BufferUtils.createFloatBuffer(verts.length+texCords.length);
		vertBuffer.put(verts);
		vertBuffer.put(texCords);
		vertBuffer.flip();
		
		int vertBufferObj = glGenBuffers();
		glBindBuffer(GL_ARRAY_BUFFER, vertBufferObj);
	    glBufferData(GL_ARRAY_BUFFER, vertBuffer, GL_STATIC_DRAW);
		glBindBuffer(GL_ARRAY_BUFFER, 0);
		
		ByteBuffer texBuffer = BufferUtils.createByteBuffer(texData.length);
		texBuffer.put(texData);
		texBuffer.flip();
		
		// Create the texture		

		int texture = glGenTextures();
		glBindTexture(GL_TEXTURE_2D, texture);
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, texBuffer);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
	    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
	    glBindTexture(GL_TEXTURE_2D, 0);
	    
		// get the Uniform location

	    int textureUnif = glGetUniformLocation(program, "tex");
	    
		// set up the sampler

		int sampler = glGenSamplers();
		glSamplerParameteri(sampler, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
		glSamplerParameteri(sampler, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
		glSamplerParameteri(sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
		glSamplerParameteri(sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
		
		int i = 0;   // using the first texture
		
		// Put the texture into the uniform

		glUseProgram(program);
		glUniform1i(textureUnif, i);
		glUseProgram(0);
		
		// make the VAO

		int vao = glGenVertexArrays();
		glBindVertexArray(vao);
		glBindBuffer(GL_ARRAY_BUFFER, vertBufferObj);
		glEnableVertexAttribArray(0);
		glVertexAttribPointer(0, 4, GL_FLOAT, false, 0, 0);
		glEnableVertexAttribArray(1);
		glVertexAttribPointer(1, 2, GL_FLOAT, false, 0, Float.SIZE/8 * verts.length);
		glBindVertexArray(0);

		// Finally reader to render!! :)
		
		while(!Display.isCloseRequested()) {
			
			glClear(GL_COLOR_BUFFER_BIT);
			
			// Set up the context
			glUseProgram(program);
			glActiveTexture(GL_TEXTURE0 + i);
			glBindTexture(GL_TEXTURE_2D, texture);
			glBindSampler(i, sampler);
			glBindVertexArray(vao);
			glDrawArrays(GL_QUADS, 0, 4);
			// Clean up
			glBindSampler(i, 0);
			glBindTexture(GL_TEXTURE_2D, 0);
			glBindVertexArray(0);
			glUseProgram(0);
			
			Display.update();
			Display.sync(30);
		}
		
	}

}

Any help is appreciated! ;D (EDIT: I added some comments to the code)

#2

You are not checking the compile, link, or validate status at any time. You need to do that after each of those steps using glGetShader/glGetProgram, and print the appropriate log using glGetShaderInfoLog/glGetProgramInfoLog in the case of an error.

#3

Thank you for the tip! I have added the following into my code:

		int vShader = glCreateShader(GL_VERTEX_SHADER);
		glShaderSource(vShader, easyTexVert);
		glCompileShader(vShader);
		
		int success = glGetShader(vShader, GL_COMPILE_STATUS);		
		if(success != 1) {
			String s = glGetShaderInfoLog(vShader, 1024);
			System.out.println("Error Compiling Shader: "+s);
			System.exit(1);
		}
		
		int fShader = glCreateShader(GL_FRAGMENT_SHADER);
		glShaderSource(fShader, easyTexFrag);
		glCompileShader(fShader);
		
		success = glGetShader(fShader, GL_COMPILE_STATUS);		
		if(success != 1) {
			String s = glGetShaderInfoLog(fShader, 1024);
			System.out.println("Error Compiling Shader: "+s);
			System.exit(1);
		}
		
		int program = glCreateProgram();
		glAttachShader(program, vShader);
		glAttachShader(program, fShader);
		glLinkProgram(program);
		glValidateProgram(program);
		
		success = glGetProgram(program, GL_LINK_STATUS);		
		if(success != 1) {
			String s = glGetProgramInfoLog(program, 1024);
			System.out.println("Error Linking Program: "+s);
			System.exit(1);
		}

Not sure what else to do if there is an error, aside from just exit the program.