ShaderHelper.java

/*
 * Copyright 2014 Google Inc. All Rights Reserved.

 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.cardboard.photosphere;

import android.opengl.GLES20;
import android.util.Log;

/**
 * @author Sree Kumar A.V
 */
public class ShaderHelper
{
	private static final String TAG = "ShaderHelper";
	
	/** 
	 * Helper function to compile a shader.
	 * 
	 * @param shaderType The shader type.
	 * @param shaderSource The shader source code.
	 * @return An OpenGL handle to the shader.
	 */
	public static int compileShader(final int shaderType, final String shaderSource) 
	{
		int shaderHandle = GLES20.glCreateShader(shaderType);

		if (shaderHandle != 0) 
		{
			// Pass in the shader source.
			GLES20.glShaderSource(shaderHandle, shaderSource);

			// Compile the shader.
			GLES20.glCompileShader(shaderHandle);

			// Get the compilation status.
			final int[] compileStatus = new int[1];
			GLES20.glGetShaderiv(shaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);

			// If the compilation failed, delete the shader.
			if (compileStatus[0] == 0) 
			{
				Log.e(TAG, "Error compiling shader: " + GLES20.glGetShaderInfoLog(shaderHandle));
				GLES20.glDeleteShader(shaderHandle);
				shaderHandle = 0;
			}
		}

		if (shaderHandle == 0)
		{			
			throw new RuntimeException("Error creating shader.");
		}
		
		return shaderHandle;
	}
	
	/**
	 * Helper function to compile and link a program.
	 * 
	 * @param vertexShaderHandle An OpenGL handle to an already-compiled vertex shader.
	 * @param fragmentShaderHandle An OpenGL handle to an already-compiled fragment shader.
	 * @param attributes Attributes that need to be bound to the program.
	 * @return An OpenGL handle to the program.
	 */
	public static int createAndLinkProgram(final int vertexShaderHandle, final int fragmentShaderHandle, final String[] attributes) 
	{
		int programHandle = GLES20.glCreateProgram();
		
		if (programHandle != 0) 
		{
			// Bind the vertex shader to the program.
			GLES20.glAttachShader(programHandle, vertexShaderHandle);			

			// Bind the fragment shader to the program.
			GLES20.glAttachShader(programHandle, fragmentShaderHandle);
			
			// Bind attributes
			if (attributes != null)
			{
				final int size = attributes.length;
				for (int i = 0; i < size; i++)
				{
					GLES20.glBindAttribLocation(programHandle, i, attributes[i]);
				}						
			}
			
			// Link the two shaders together into a program.
			GLES20.glLinkProgram(programHandle);

			// Get the link status.
			final int[] linkStatus = new int[1];
			GLES20.glGetProgramiv(programHandle, GLES20.GL_LINK_STATUS, linkStatus, 0);

			// If the link failed, delete the program.
			if (linkStatus[0] == 0) 
			{				
				Log.e(TAG, "Error compiling program: " + GLES20.glGetProgramInfoLog(programHandle));
				GLES20.glDeleteProgram(programHandle);
				programHandle = 0;
			}
		}
		
		if (programHandle == 0)
		{
			throw new RuntimeException("Error creating program.");
		}
		
		return programHandle;
	}
}