I am trying to create a triangle in openGL 2.0 but some some reason background is shows up but no triangle. I am following this tutorial: http://developer.android.com/training/graphics/opengl/environment.html
i have the same code as on tutorial but for some reason the triangle is not showing up.
may be i missed some thing or i am doing some thing wrong?
i have two class.
GlRender.java
GLTriangle.java
i think the problem is in GLTriangle draw method.
public class GlRender implements Renderer {
private GLTriangle glTriangleObj;
private final float[] mModelMatrix = new float[16];
private final float[] mProjectionMatrix = new float[16];
private final float[] mViewMatrix = new float[16];
private final float[] mRotationMatrix = new float[16];
/************************/
/*** create() method ***/
/************************/
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
// Set the background color
// 0 to 1
// 1 = no transparent
GLES20.glClearColor(0.8f, 0.2f, 0.2f, 1f);
gl.glClearDepthf(1f);
glTriangleObj = new GLTriangle();
// glSquare = new Square(); //etc...
// postion the eye behind the origin
final float eyeX = 0.0f;
final float eyeY = 0.0f;
final float eyeZ = 1.5f;
// we are looking toward the distance
final float lookX = 0.0f;
final float lookY = 0.0f;
final float lookZ = -5.0f;
// Set our up vector. This is where our head would be pointing were we
// holding the camera.
final float upX = 0.0f;
final float upY = 1.0f;
final float upZ = 0.0f;
// Set the view matrix. This matrix can be said to represent the camera
// position.
// NOTE: In OpenGL 1, a ModelView matrix is used, which is a combination
// of a model and
// view matrix. In OpenGL 2, we can keep track of these matrices
// separately if we choose.
Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY,
lookZ, upX, upY, upZ);
}
/********************/
/*** paint method ***/
/********************/
@Override
public void onDrawFrame(GL10 gl) {
// Redraw background color
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
// do a complete rotation every 10 seconds
// long time = SystemClock.uptimeMillis() % 10000L;
// float angleInDegree = (360.0f / 10000.0f) * ((int) time);
// draw the triangle face straight on
// Matrix.setIdentityM(mModelMatrix, 0);
// Matrix.rotateM(mModelMatrix, 0, angleInDegree, 0.0f, 0.0f, 1.0f);
// Set the camera position (View matrix)
Matrix.setLookAtM(mViewMatrix, 0, 0, -2, 0, 0f, 0f, 0f, 0f, 2.0f, 0.0f);
// Calculate the projection and view transformation
Matrix.multiplyMM(mModelMatrix, 0, mProjectionMatrix, 0, mViewMatrix, 0);
glTriangleObj.draw(mModelMatrix);
}
/*****************************/
/*** landscape to portrait ***/
/*****************************/
@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
if (height == 0)
height = 1;
// Set the OpenGL viewport to the same size as the surface.
GLES20.glViewport(0, 0, width, height);
// while the width will vary as per aspect ratio.
final float ratio = (float) width / height;
final float left = -ratio;
final float right = ratio;
final float bottom = -1.0f;
final float top = 1.0f;
final float near = 1.0f;
final float far = 25.0f;
Matrix.frustumM(mProjectionMatrix, 0, left, right, bottom, top, near,
far);
}
}
GLTriangle.java
[CODE]public class GLTriangle {
// always same
private final String vertexShaderCode = "attribute vec4 vPosition;"
+ "void main() {" + " gl_Position = vPosition;" + "}";
private final String fragmentShaderCode = "precision mediump float;"
+ "uniform vec4 vColor;" + "void main() {"
+ " gl_FragColor = vColor;" + "}";
// always start at zero when ploting a point as defult
// trinagle Coordinates - vertex = 3(x y z)
private float trinagleCoords[] = { 0f, 1f, // V 0 - top
1f, -1, // V 1 - right bottom
-1f, 1f // V 2 - left bottom
};
private int COORDS_PER_VERTEX = 2; // number of points
private FloatBuffer vertexBuffer;
private short[] drawOrder = { 0, 1, 2 }; // order
private ShortBuffer orderBuffer;
float color[] = { 0.5f, 1f, 0f, 1f };
private int vertexCount = trinagleCoords.length / COORDS_PER_VERTEX;
private int vertexStride = COORDS_PER_VERTEX * 4; // bytes per vertex
// used to pass in the transformation matrix
private final int mProgram;
// used to pass in model poition information
private int mPositionHandle;
// used to pass inmodel color information
private int mColorHandle;
private int mMVPMatrixHandle;
public GLTriangle() {
// vertices - has to be 4
ByteBuffer byteBuffer = ByteBuffer
.allocateDirect(trinagleCoords.length * 4);
byteBuffer.order(ByteOrder.nativeOrder());
vertexBuffer = byteBuffer.asFloatBuffer();
vertexBuffer.put(trinagleCoords);
vertexBuffer.position(0);
// draw order - has to be 2
ByteBuffer pointByteBuffer = ByteBuffer
.allocateDirect(drawOrder.length * 2);
pointByteBuffer.order(ByteOrder.nativeOrder());
orderBuffer = pointByteBuffer.asShortBuffer();
orderBuffer.put(drawOrder);
orderBuffer.position(0);
// shader - always same
int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER,
fragmentShaderCode);
// create empty OpenGL ES Program
mProgram = GLES20.glCreateProgram();
// add the vertex shader to program
GLES20.glAttachShader(mProgram, vertexShader);
// add the fragment shader to program
GLES20.glAttachShader(mProgram, fragmentShader);
// creates OpenGL ES program executables
GLES20.glLinkProgram(mProgram);
}
/************/
/*** same ***/
/************/
public static int loadShader(int type, String shaderCode) {
// create a vertex shader type (GLES20.GL_VERTEX_SHADER)
// or a fragment shader type (GLES20.GL_FRAGMENT_SHADER)
int shader = GLES20.glCreateShader(type);
// add the source code to the shader and compile it
GLES20.glShaderSource(shader, shaderCode);
GLES20.glCompileShader(shader);
return shader;
}
public void draw(float[] mModelMatrix) {
// Add program to OpenGL environment
GLES20.glUseProgram(mProgram);
// get handle to vertex shader's vPosition member
mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
// Enable a handle to the triangle vertices
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Prepare the triangle coordinate data
GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX,
GLES20.GL_FLOAT, false, vertexStride, vertexBuffer);
// get handle to fragment shader's vColor member
mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
// Set color for drawing the triangle
GLES20.glUniform4fv(mColorHandle, 1, color, 0);
// Draw the triangle
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);
// Disable vertex array
GLES20.glDisableVertexAttribArray(mPositionHandle);
// get handle to shape's transformation matrix
mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
// Apply the projection and view transformation
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mModelMatrix, 0);
// Draw the triangle
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);
}
}