Question

谁能告诉我如何使用

GL11.glreadpixels（）

在lwjgl中的

以获得鼠标投射的射线的z深度？在将其转换为ray之前，我可以得到x，y和视图的视图

float x = Mouse.getX();
float y = Mouse.getY();

但是我不知道如何使用glreadpixels 因为当我使用它没有任何意义计算鼠标点和计算鼠标光线都给出相同的结果

public static float getZDepth(int x, int y)
{
   ByteBuffer zdepth = allocBytes(SIZE_FLOAT);
   GL11.glReadPixels(x, y, 1, 1, GL11.GL_DEPTH_COMPONENT, GL11.GL_FLOAT, zdepth);
   return ( (float) (zdepth.getFloat(0)));
}
private Vector3f calculateMouseRay() {
    float mouseX = Mouse.getX();
    float mouseY = Mouse.getY();
    Vector2f normalizedCoords = getNormalisedDeviceCoordinates(mouseX, mouseY);
    Vector4f clipCoords = new Vector4f(normalizedCoords.x, normalizedCoords.y, -1.0f, 1.0f);
    Vector4f eyeCoords = toEyeCoords(clipCoords);
    Vector3f worldRay = toWorldCoords(eyeCoords);
    return worldRay;
}

private Vector3f calculateMousePoint() {
    float mouseX = Mouse.getX();
    float mouseY = Mouse.getY();
    float mouseZ = getZDepth((int)mouseX,(int) mouseY);

    Vector2f normalizedCoords = getNormalisedDeviceCoordinates(mouseX, mouseY);
    Vector4f clipCoords = new Vector4f(normalizedCoords.x, normalizedCoords.y, mouseZ, 1.0f);
    Vector4f eyeCoords = toEyeCoords2(clipCoords);
    Vector3f worldRay = toWorldCoords(eyeCoords);
    return worldRay;
}
private Vector3f toWorldCoords(Vector4f eyeCoords) {
    Matrix4f invertedView = Matrix4f.invert(viewMatrix, null);
    Vector4f rayWorld = Matrix4f.transform(invertedView, eyeCoords, null);
    Vector3f mouseRay = new Vector3f(rayWorld.x, rayWorld.y, rayWorld.z);
    mouseRay.normalise();
    return mouseRay;
}

private Vector4f toEyeCoords(Vector4f clipCoords) {
    Matrix4f invertedProjection = Matrix4f.invert(projectionMatrix, null);
    Vector4f eyeCoords = Matrix4f.transform(invertedProjection, clipCoords, null);
    return new Vector4f(eyeCoords.x, eyeCoords.y, -1f, 0f);
}
private Vector4f toEyeCoords2(Vector4f clipCoords) {
    Matrix4f invertedProjection = Matrix4f.invert(projectionMatrix, null);
    Vector4f eyeCoords = Matrix4f.transform(invertedProjection, clipCoords, null);
    return new Vector4f(eyeCoords.x, eyeCoords.y, eyeCoords.z, 0f);
}
private Vector2f getNormalisedDeviceCoordinates(float mouseX, float mouseY) {
    float x = (2.0f * mouseX) / Display.getWidth() - 1f;
    float y = (2.0f * mouseY) / Display.getHeight() - 1f;
    return new Vector2f(x, y);
}

Answer 1

From the documentation， x，y 和_width，height代表要拍摄的区域。 type 是数据的类型，然后 data 是结果。

最后，最重要的是 format 参数：您可以选择要检索的内容。对您来说，它将是GL_DEPTH_COMPONENT：

float zmouse;
GL11.glReadnPixels(xmouse, ymouse, 1, 1, GL11.GL_DEPTH_COMPONENT, GL11.GL_FLOAT, zmouse)

您具有Z深度，现在必须将其转换为良好的空间。实际上，这是剪辑空间，我想您会得到一个摄像头空间。因此，您必须将“鼠标”点乘以投影和视图矩阵的倒数，例如realPoint = inverse(projection * view * model) * (xmouse, ymousen, zmouse)。

最后，realPoint是3D空间中的点。

以您的代码为例，这应该可以完成工作：

public static float getZDepth(int x, int y)
{
   ByteBuffer zdepth = allocBytes(SIZE_FLOAT);
   GL11.glReadPixels(x, y, 1, 1, GL11.GL_DEPTH_COMPONENT, GL11.GL_FLOAT, zdepth);
   return ( (float) (zdepth.getFloat(0)));
}

private Vector3f calculateMousePoint(Vector3f point) {
    float x = Mouse.getX();
    float y = Mouse.getY();
    float z = getZDepth((int)mouseX,(int) mouseY);
    return project(new Vector3f(x,y,z), new Vector4f(0,0,Display.getWidth(), Display.getHeight()));
}
private Vector3f calculateFarPoint(Vector3f point) {
    float x = Mouse.getX();
    float y = Mouse.getY();
    return project(new Vector3f(x,y,1.), new Vector4f(0,0,Display.getWidth(), Display.getHeight()));
}
// Code translated from GLM_GTC_matrix_transform 
//(https://glm.g-truc.net/0.9.2/api/a00245.html#gac38d611231b15799a0c06c54ff1ede43)
private Vector3f project(Vector3f point, Vector4f viewport)
{
    Matrix4f Inverse = Matrix4f.invert(projectionMatrix * viewMatrix)
    Vector4f tmp = new Vector4f(point.x, point.y, point.z, 1.f);
    tmp.x = (tmp.x - viewport.x) / viewport.z;
    tmp.y = (tmp.y - viewport.y) / viewport.w;
    tmp = tmp * 2.0 - 1.0;
    Vector4f obj = Inverse * tmp;
    obj /= obj.w;
    return new Vector3f(obj.x, obj.y, obj.z);
}

如何使用glreadpixels（）获得z深度

1 个答案: