[英]ARCore – How to place a Real World object in front of a 3d model?
[英]In ARCore using java, how can I draw a 3D triangle/line in my world
OpenGL / ArCore的全新概念,存在一些問題。 我只想在錨點附近畫一個三角形,但不知道該怎么做。 同時,我還想畫一條線,該線有一個原點和一個方向向量。
我正在使用Google的ARCore示例項目作為基礎。 我可以使用他們的OpenGL教程和以下Triangle類在此屏幕上繪制2D三角形:
private final String vertexShaderCode =
// This matrix member variable provides a hook to manipulate
// the coordinates of the objects that use this vertex shader
"uniform mat4 uMVPMatrix;" +
"attribute vec4 vPosition;" +
"void main() {" +
// the matrix must be included as a modifier of gl_Position
// Note that the uMVPMatrix factor *must be first* in order
// for the matrix multiplication product to be correct.
" gl_Position = uMVPMatrix * vPosition;" +
"}";
private final String fragmentShaderCode =
"precision mediump float;" +
"uniform vec4 vColor;" +
"void main() {" +
" gl_FragColor = vColor;" +
"}";
private final FloatBuffer vertexBuffer;
private final int mProgram;
private int mPositionHandle;
private int mColorHandle;
private int mMVPMatrixHandle;
// number of coordinates per vertex in this array
static final int COORDS_PER_VERTEX = 3;
static float triangleCoords[] = {
// in counterclockwise order:
0.0f, 0.622008459f, 0.0f, // top
-0.5f, -0.311004243f, 0.0f, // bottom left
0.5f, -0.311004243f, 0.0f // bottom right
};
private final int vertexCount = triangleCoords.length / COORDS_PER_VERTEX;
private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex
float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 0.0f };
/**
* Sets up the drawing object data for use in an OpenGL ES context.
*/
public Triangle() {
// initialize vertex byte buffer for shape coordinates
ByteBuffer bb = ByteBuffer.allocateDirect(
// (number of coordinate values * 4 bytes per float)
triangleCoords.length * 4);
// use the device hardware's native byte order
bb.order(ByteOrder.nativeOrder());
// create a floating point buffer from the ByteBuffer
vertexBuffer = bb.asFloatBuffer();
// add the coordinates to the FloatBuffer
vertexBuffer.put(triangleCoords);
// set the buffer to read the first coordinate
vertexBuffer.position(0);
// prepare shaders and OpenGL program
int vertexShader = MyGLRenderer.loadShader(
GLES20.GL_VERTEX_SHADER, vertexShaderCode);
int fragmentShader = MyGLRenderer.loadShader(
GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
mProgram = GLES20.glCreateProgram(); // create empty OpenGL Program
GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program
GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program
GLES20.glLinkProgram(mProgram); // create OpenGL program executables
}
/**
* Encapsulates the OpenGL ES instructions for drawing this shape.
*
* @param mvpMatrix - The Model View Project matrix in which to draw
* this shape.
*/
public void draw(float[] mvpMatrix) {
// 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);
// get handle to shape's transformation matrix
mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
MyGLRenderer.checkGlError("glGetUniformLocation");
// Apply the projection and view transformation
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);
MyGLRenderer.checkGlError("glUniformMatrix4fv");
// Draw the triangle
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);
// Disable vertex array
GLES20.glDisableVertexAttribArray(mPositionHandle);
}
更改trianglecoords變量內的z值根本不會影響繪制三角形,因此我對如何進行處理感到困惑。
如果您想知道為什么,我正在嘗試進行射線三角相交測試; 它的效果不是很好,並且想測試一個三角形的工作方式。 我為此煩惱不已,這種看似簡單的動作多么復雜,這真讓我很煩。
提前致謝!
編輯我知道GL很難涉足ARCore。 我的任務是與ARCore一起玩,而且由於我還將GL用於個人項目,所以我真的很想了解它,而不是使用Unity / Unreal。
您可以通過設置正確的參數來使用ShapeFactory.makeCylinder
模擬一條線。 但是,這在OpenGL中不會出現,但是對於簡單的一行來說肯定會減少開銷。
我的方法是獲取兩行結尾的起始詞和結束詞coodrinate點。 然后計算直線的方向和距離,使用該距離作為圓柱體的長度。 將線放置在距離的中間,然后相應地旋轉以適合實際的起點和終點。
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