编辑：问题已解决！ 所以我一直在浏览Android的官方OpenGL ES 2教程，并且我已经完成了涉及绘制形状的部分，但我似乎无法找到一个正方形。它会绘制一个直角三角形。
我已经包含了用于定义和绘制形状的代码，几乎完全从教程中复制。 Renderer类只是创建一个这种形状的实例并调用draw方法。
由于某种原因，本教程没有给出vertexStride和vertexCount的值/声明，所以我在那里的那些是有根据的猜测。我已经为vertexCount（1到12）尝试了几个值，但都没有工作。
提前致谢。
public class Square {
private FloatBuffer vertexBuffer;
private ShortBuffer drawListBuffer;
// number of coordinates per vertex in this array
static final int COORDS_PER_VERTEX = 3;
static float squareCoords[] = { -0.5f, 0.5f, 0.0f, // top left
-0.5f, -0.5f, 0.0f, // bottom left
0.5f, -0.5f, 0.0f, // bottom right
0.5f, 0.5f, 0.0f }; // top right
private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices
float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };
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;" +
"}";
int mProgram;
static final int vertexStride = COORDS_PER_VERTEX * 4;
static final int vertexCount = 4;
public Square() {
// initialize vertex byte buffer for shape coordinates
ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4); // (# of coordinate values * 4 bytes per float)
bb.order(ByteOrder.nativeOrder());
vertexBuffer = bb.asFloatBuffer();
vertexBuffer.put(squareCoords);
vertexBuffer.position(0);
// initialize byte buffer for the draw list
ByteBuffer dlb = ByteBuffer.allocateDirect(drawOrder.length * 2); // (# of coordinate values * 2 bytes per short)
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
mProgram = GLES20.glCreateProgram(); // create empty OpenGL ES Program
GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program
GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program
GLES20.glLinkProgram(mProgram); // creates OpenGL ES program executables
}
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() {
// Add program to OpenGL ES environment
GLES20.glUseProgram(mProgram);
// get handle to vertex shader's vPosition member
int 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
int 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);
}
}
答案 0 :(得分：26)
vertexCount = squareCoords.length/COORDS_PER_VERTEX; //Vertex count is the array divided by the size of the vertex ex. (x,y) or (x,y,z)
vertexStride = COORDS_PER_VERTEX * 4; //4 are how many bytes in a float
如果这对您有用，请告诉我，祝您好运。
我认为您还缺少用于将3D空间转换为2D屏幕空间的ModelViewProjection矩阵。应该通过绘制函数draw(float[] mvpMatrix)传入mvpMatrix
忘记提及你也应该使用DrawElements(...)（在例子中使用）如果你不需要计数或步幅，只需要idicies数组和绘图缓冲区的长度。
// Get handle to shape's transformation matrix
mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
// Apply the projection and view transformation
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);
// Draw the square
GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length,
GLES20.GL_UNSIGNED_SHORT, drawListBuffer);
答案 1 :(得分：13)
The tutorial is missing some steps: the final code for the square is here.
The example was intended to use glDrawElements instead of glDrawArrays which is indicated by the presence of the line: private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices.
This array specifies the desired vertices of 2 triangles. 0, 1 and 2 for the first. Then 0, 2 and 3 for the second. GL_TRANGLE_FAN just happens to work because it will draw the next triangle using the first vertex in the buffer, the last vertex used in previous triangle and the next vertex. For the second triangle this is 0, 2 and 3. Then 0, 3 and 4, etc. Had vertex 2 been 5, 5 and vertex 3 been -5, 5, the resulting fan would not have been a square.
Replace these lines:
// Draw the triangle
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);
With these:
// Draw the square
GLES20.glDrawElements(
GLES20.GL_TRIANGLES, drawOrder.length,
GLES20.GL_UNSIGNED_SHORT, drawListBuffer);
答案 2 :(得分：-1)
@Jon W 我认为GL_TRIANGLES＆amp; GL_TRIANGLE_FAN在图片中说明：
