VertexAttribute.java

/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * 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.badlogic.gdx.graphics;

import com.badlogic.gdx.graphics.VertexAttributes.Usage;
import com.badlogic.gdx.graphics.glutils.ShaderProgram;

/**
 * A single vertex attribute defined by its {@link Usage}, its number of components and its shader alias. The Usage is
 * needed for the fixed function pipeline of OpenGL ES 1.x. Generic attributes are not supported in the fixed function
 * pipeline. The number of components defines how many components the attribute has. The alias defines to which shader
 * attribute this attribute should bind. The alias is used by a {@link Mesh} when drawing with a {@link ShaderProgram}.
 * The alias can be changed at any time.
 * 
 * @author mzechner
 */
public final class VertexAttribute {
	/** the attribute {@link Usage} **/
	public final int usage;
	/** the number of components this attribute has **/
	public final int numComponents;
	/** the offset of this attribute in bytes, don't change this! **/
	public int offset;
	/** the alias for the attribute used in a {@link ShaderProgram} **/
	public String alias;

	/**
	 * Constructs a new VertexAttribute.
	 * 
	 * @param usage
	 *            the usage, used for the fixed function pipeline. Generic attributes are not supported in the fixed
	 *            function pipeline.
	 * @param numComponents
	 *            the number of components of this attribute, must be between 1 and 4.
	 * @param alias
	 *            the alias used in a shader for this attribute. Can be changed after construction.
	 */
	public VertexAttribute(int usage, int numComponents, String alias) {
		this.usage = usage;
		this.numComponents = numComponents;
		this.alias = alias;
	}

	public static VertexAttribute Position() {
		return new VertexAttribute(Usage.Position, 3, ShaderProgram.POSITION_ATTRIBUTE);
	}

	public static VertexAttribute TexCoords(int unit) {
		return new VertexAttribute(Usage.TextureCoordinates, 2, ShaderProgram.TEXCOORD_ATTRIBUTE + unit);
	}

	public static VertexAttribute Normal() {
		return new VertexAttribute(Usage.Normal, 3, ShaderProgram.NORMAL_ATTRIBUTE);
	}

	public static VertexAttribute Color() {
		return new VertexAttribute(Usage.ColorPacked, 4, ShaderProgram.COLOR_ATTRIBUTE);
	}

	public static VertexAttribute ColorUnpacked() {
		return new VertexAttribute(Usage.Color, 4, ShaderProgram.COLOR_ATTRIBUTE);
	}

	/** Tests to determine if the passed object was created with the same parameters */
	@Override
	public boolean equals(final Object obj) {
		if (!(obj instanceof VertexAttribute)) {
			return false;
		}
		final VertexAttribute other = (VertexAttribute) obj;
		return this.usage == other.usage && this.numComponents == other.numComponents && this.alias.equals(other.alias);
	}
}