OpenGL: Drawing Quad - Color fading issue
I'm trying to draw a white quad on Android with OpenGL-ES and the colors are fading.
See picture: http://img88.imageshack.us/img88/2787/tempew.png
I have tried it with int numVertices = 4;
as well, but instead of the redness I get black. What is the deal?
int numVertices = 6;
private FloatBuffer vertexBuffer, colorBuffer;
private ShortBuffer indexBuffer;
private short[] indices = { 0, 1, 2,
2, 3, 0 };
public Floor (float coords[][]) {
float vertices[] = new float[numVertices*3];
float colors[] = new float[numVertices*4];
//Set colors
for(int i=0; i < numVertices; i++){
colors[i] = 1.0f; //red
colors[i+1] = 1.0f; //grn
colors[i+2] = 1.0f; //blu
colors[i+3] = 1.0f; //alpha
}
vertices[0] = coords[0][0];
vertices[1] = coords[0][1];
vertices[2] = coords[0][2];
vertices[3] = coords[1][0];
vertices[4] = coords[1][1];
vertices[5] = coords[1][2];
vertices[6] = coords[2][0];
vertices[7] = coords[2][1];
vertices[8] = coords[2][2];
vertices[9] = coords[3][0];
vertices[10] = coords[3][1];
vertices[11] = coords[3][2];
ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
vbb.order(ByteOrder.nativeOrder());
vertexBuffer = vbb.asFloatBuffer();
vertexBuffer.put(vertices);
vertexBuffer.position(0);
ByteBuffer cbb = ByteBuffer.allocateDirect(colors.length * 4);
cbb.order(ByteOrder.nativeOrder());
colorBuffer = cbb.asFloatBuffer();
colorBuffer.put(colors);
colorBuffer.position(0);
ByteBuffer ibb = ByteBuffer.allocateDirect(indices.length * 2);
ibb.order(ByteOrder.nativeOrder());
indexBuffer = ibb.asShortBuffer();
indexBuffer.put(indices);
indexBuffer.position(0);
}
/**
* This function draws our square on screen.
* @param gl
*/
public void draw(GL10 gl) {
gl.glDisable(GL10.GL_COLOR_MATERIAL);
gl.glDisable(GL10.GL_BLEND);
gl.glDisable(GL10.GL_LIGHTING);
gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
开发者_开发问答gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glColorPointer(4, GL10.GL_FLOAT, 0, colorBuffer);
gl.glPointSize(2.0f);
gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_SHORT, indexBuffer);
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisableClientState(GL10.GL_COLOR_ARRAY);
}
}
Thanks for any help!
Figured it out. For anyone else running into how to do this, fixes needed:
int numVertices = 4;
//Set colors
for(int i=0; i < numVertices; i++){
colors[i*4] = 1.0f; //red
colors[i*4+1] = 1.0f; //grn
colors[i*4+2] = 1.0f; //blu
colors[i*4+3] = 1.0f; //alpha
}
for(int i=0; i < numVertices; i++){
colors[i] = 1.0f; //red
colors[i+1] = 1.0f; //grn
colors[i+2] = 1.0f; //blu
colors[i+3] = 1.0f; //alpha
}
This does not do what you think it does. You need to write i += 4
.
Otherwise, you initialize numVertices/4 + 4 components instead of numVertices*4 as you intended.
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