LWJGL - Shader loading - Invalid value

Newbie & Debugging Questions
#1

I have been reading the red book on open gl and to help me understand the tutorials I have been rewriting them into Java using LWJGL.

I’ve have gotten stuck on one of the tutorials in chapter 3 where the shader will not load.
The goal of the tutorial is to render four triangles using four different buffers, sub-buffer, arrays, elements.

Here is the init code which sets up the triangles and the shaders.


	private void init()
	{
		// A single triangle
		FloatBuffer vertexPositions = BufferUtils.createFloatBuffer(16);
		vertexPositions.put(new float[] { -1.0f, -1.0f, 0.0f, 1.0f });
		vertexPositions.put(new float[] { 1.0f, -1.0f, 0.0f, 1.0f });
		vertexPositions.put(new float[] { -1.0f, 1.0f, 0.0f, 1.0f });
		vertexPositions.put(new float[] { -1.0f, -1.0f, 0.0f, 1.0f });
		vertexPositions.flip();

		// A colours for the triangle
		FloatBuffer vertexColours = BufferUtils.createFloatBuffer(16);
		vertexColours.put(new float[] { 1.0f, 1.0f, 1.0f, 1.0f });
		vertexColours.put(new float[] { 1.0f, 1.0f, 0.0f, 1.0f });
		vertexColours.put(new float[] { 1.0f, 0.0f, 1.0f, 1.0f });
		vertexColours.put(new float[] { 0.0f, 1.0f, 1.0f, 1.0f });
		vertexColours.flip();

		// indices for the triangle strips
		final byte[] vertexIndices = new byte[] { 0, 1, 2 };
		ByteBuffer indicesBuffer = BufferUtils.createByteBuffer(vertexIndices.length);
		indicesBuffer.put(vertexIndices);
		indicesBuffer.flip();

		// Set up the element array buffer
		elementBufferId = GL15.glGenBuffers();
		GL15.glBindBuffer(GL15.GL_ELEMENT_ARRAY_BUFFER, elementBufferId);
		GL15.glBufferData(GL15.GL_ELEMENT_ARRAY_BUFFER, indicesBuffer, GL15.GL_STATIC_DRAW);

		// Set up the vertex attributes
		vaoId = GL30.glGenVertexArrays();
		GL30.glBindVertexArray(vaoId);

		vboId = GL15.glGenBuffers();
		GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, vboId);
		GL15.glBufferData(GL15.GL_ARRAY_BUFFER, vertexPositions.capacity() + vertexColours.capacity(), GL15.GL_STATIC_DRAW);

		GL15.glBufferSubData(GL15.GL_ARRAY_BUFFER, 0, vertexPositions);
		GL15.glBufferSubData(GL15.GL_ARRAY_BUFFER, vertexPositions.capacity(), vertexColours);

		GL20.glVertexAttribPointer(0, 2, GL11.GL_FLOAT, false, 0, 0L);
		GL20.glVertexAttribPointer(1, 4, GL11.GL_FLOAT, false, 0, vertexPositions.capacity());
		GL20.glEnableVertexAttribArray(0);
		GL20.glEnableVertexAttribArray(1);
		// create program

		Matrix4f model_matrix = new Matrix4f();
		Matrix4f projection_matrix = new Matrix4f();

		vertexShader = ShaderUtils.loadShader("src/dw/redbook/tutorials/ex002drawingcommands/primitive_restart.vs.glsl", GL20.GL_VERTEX_SHADER);
		fragmentShader = ShaderUtils.loadShader("src/dw/redbook/tutorials/ex002drawingcommands/primitive_restart.fs.glsl", GL20.GL_FRAGMENT_SHADER);
		// vertexShader = ShaderUtils.loadShader("src/dw/redbook/tutorials/ex002drawingcommands/triangles.vs", GL20.GL_VERTEX_SHADER);
		// fragmentShader = ShaderUtils.loadShader("src/dw/redbook/tutorials/ex002drawingcommands/triangles.fs", GL20.GL_FRAGMENT_SHADER);

		renderProgramId = GL20.glCreateProgram();
		glAttachShader(renderProgramId, vertexShader);
		glAttachShader(renderProgramId, fragmentShader);

		glLinkProgram(renderProgramId);
		glValidateProgram(renderProgramId);
		GL20.glUseProgram(renderProgramId);

		// Create a FloatBuffer with the proper size to store our matrices later
		matrix44Buffer = BufferUtils.createFloatBuffer(16);

	}

If you need to see anything else then I can paste it.

The shader it fails to load is

#version 330

uniform mat4 model_matrix;
uniform mat4 projection_matrix;

layout (location = 0) in vec4 position;
layout (location = 1) in vec4 color;

out vec4 vs_fs_color;

void main(void)
{
    vs_fs_color = color;
    gl_Position = projection_matrix * (model_matrix * position);
}
#2

Where is your shader loading code?

#3

Ah yes,
The shaderloader code is very similar that is on the LWJGL wiki

package dw.shader;

import static org.lwjgl.opengl.GL11.GL_FALSE;
import static org.lwjgl.opengl.GL20.GL_COMPILE_STATUS;
import static org.lwjgl.opengl.GL20.glCompileShader;
import static org.lwjgl.opengl.GL20.glCreateShader;
import static org.lwjgl.opengl.GL20.glGetShaderi;
import static org.lwjgl.opengl.GL20.glShaderSource;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

import org.lwjgl.opengl.Display;

import dw.game.GameUtils;

public class ShaderUtils
{

	public static int loadShader(String filename, int shaderType)
	{
		System.out.println("attempting to load:=" + filename);
		StringBuilder shaderSource = new StringBuilder();
		int shaderId = glCreateShader(shaderType);

		BufferedReader reader = null;
		try
		{
			reader = new BufferedReader(new FileReader(filename));
			String line;
			while ((line = reader.readLine()) != null)
			{
				// System.out.println(line);
				shaderSource.append(line).append('\n');
			}
		} catch (IOException e)
		{
			System.err.println("Fragment shader wasn't loaded properly.");
			Display.destroy();
			System.exit(1);
		} finally
		{
			if (reader != null)
			{
				try
				{
					reader.close();
				} catch (IOException e)
				{
					e.printStackTrace();
				}
			}
		}

		glShaderSource(shaderId, shaderSource);
		glCompileShader(shaderId);
		if (glGetShaderi(shaderId, GL_COMPILE_STATUS) == GL_FALSE)
		{
			System.err.println("Fragment shader wasn't able to be compiled correctly.");
			System.exit(1);
		}

		System.out.println("loaded:=" + filename);
		GameUtils.exitOnGLError("loadShader");
		return shaderId;
	}

}
#4

You are getting an [icode]IOException[/icode] which means that the file is not found. Try checking your class path.

#5

I’m not sure it is to do with not finding the files.

The console does manage to display the system.out at the end of the load shader method.
But all I get from the console is.

Attempting to load:=src/dw/redbook/tutorials/ex002drawingcommands/primitive_restart.vs.glsl
loaded:=src/dw/redbook/tutorials/ex002drawingcommands/primitive_restart.vs.glsl
ERROR - loadShader: Invalid value

Interestingly if I load the shaders at the start of the method then the “ERROR” message doesn’t appear until I close the display window.

#6

OpenGL’s [icode]glGetError()[/icode] function returns last generated error, not the error from the previous function. Try adding calls to [icode]GameUtils.exitOnGLError()[/icode] before and after every OpenGL call to determine from where the error comes from.

#7

Your right the error is thrown before the loadShader method.
I’ll post the solution when I find, but I have a better chance of finding it now thanks for your help.

#8

It appears that the vertexPosition and vertexColour’s FloatBuffer did not need to be flipped.
That stopped generating the error.


		// A single triangle
		FloatBuffer vertexPositions = BufferUtils.createFloatBuffer(16);
		vertexPositions.put(new float[] { -1.0f, -1.0f, 0.0f, 1.0f });
		vertexPositions.put(new float[] { 1.0f, -1.0f, 0.0f, 1.0f });
		vertexPositions.put(new float[] { -1.0f, 1.0f, 0.0f, 1.0f });
		vertexPositions.put(new float[] { -1.0f, -1.0f, 0.0f, 1.0f });
		// vertexPositions.flip();

		// A colours for the triangle
		FloatBuffer vertexColours = BufferUtils.createFloatBuffer(16);
		vertexColours.put(new float[] { 1.0f, 1.0f, 1.0f, 1.0f });
		vertexColours.put(new float[] { 1.0f, 1.0f, 0.0f, 1.0f });
		vertexColours.put(new float[] { 1.0f, 0.0f, 1.0f, 1.0f });
		vertexColours.put(new float[] { 0.0f, 1.0f, 1.0f, 1.0f });
		// vertexColours.flip();

I can start looking at making each triangle appear now.

#9

Flipping is absolutely necessary for OpenGL to read the data from it. That is clearly not the case.