samples/sdk-hellovr/src/main/java/com/google/vr/sdk/samples/hellovr/TexturedMesh.java

/*
 * Copyright 2018 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.google.vr.sdk.samples.hellovr;

import android.content.Context;
import android.opengl.GLES20;
import de.javagl.obj.Obj;
import de.javagl.obj.ObjData;
import de.javagl.obj.ObjReader;
import de.javagl.obj.ObjUtils;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.nio.ShortBuffer;

/** Renders an object loaded from an OBJ file. */
/* package */ class TexturedMesh {
  private static final String TAG = "TexturedMesh";

  private final FloatBuffer vertices;
  private final FloatBuffer uv;
  private final ShortBuffer indices;
  private final int positionAttrib;
  private final int uvAttrib;

  /**
   * Initializes the mesh from an .obj file.
   *
   * @param context Context for loading the .obj file.
   * @param objFilePath Path to the .obj file.
   * @param positionAttrib The position attribute in the shader.
   * @param uvAttrib The UV attribute in the shader.
   */
  public TexturedMesh(Context context, String objFilePath, int positionAttrib, int uvAttrib)
      throws IOException {
    InputStream objInputStream = context.getAssets().open(objFilePath);
    Obj obj = ObjUtils.convertToRenderable(ObjReader.read(objInputStream));
    objInputStream.close();

    IntBuffer intIndices = ObjData.getFaceVertexIndices(obj, 3);
    vertices = ObjData.getVertices(obj);
    uv = ObjData.getTexCoords(obj, 2);

    // Convert int indices to shorts (GLES doesn't support int indices)
    indices =
        ByteBuffer.allocateDirect(2 * intIndices.limit())
            .order(ByteOrder.nativeOrder())
            .asShortBuffer();
    while (intIndices.hasRemaining()) {
      indices.put((short) intIndices.get());
    }
    indices.rewind();

    this.positionAttrib = positionAttrib;
    this.uvAttrib = uvAttrib;
  }

  /**
   * Draws the mesh. Before this is called, u_MVP should be set with glUniformMatrix4fv(), and a
   * texture should be bound to GL_TEXTURE0.
   */
  public void draw() {
    GLES20.glEnableVertexAttribArray(positionAttrib);
    GLES20.glVertexAttribPointer(positionAttrib, 3, GLES20.GL_FLOAT, false, 0, vertices);
    GLES20.glEnableVertexAttribArray(uvAttrib);
    GLES20.glVertexAttribPointer(uvAttrib, 2, GLES20.GL_FLOAT, false, 0, uv);
    GLES20.glDrawElements(GLES20.GL_TRIANGLES, indices.limit(), GLES20.GL_UNSIGNED_SHORT, indices);
  }
}