java - Libgdx 计算 2d 中的 PerspectiveCamera View

Question

我需要计算二维相机 View 边界，x y 宽度和高度

在这个屏幕截图中，网格是每个1个单位，我需要计算3D View 的边界框，在上面的示例图像中，结果应该是:

float x = -3;
float y = 0;
float width = 14;
float height = 6;

Answer 1

假设你的相机始终俯视你的世界，因此地平线不可见，并且相机始终与 map 的 Y 轴平行，因此水平线永远不会弯曲，我认为这是计算 View 内最远线的宽度的问题，因为这是透视将向您显示最多水平瓷砖的地方。这将为您提供完全覆盖平截头体的平铺 map 的矩形区域，尽管您将在近角处绘制一些额外的图 block 。

private final Ray tmpRay = new Ray();
private final Vector3 tmpVec = new Vector3();
private final Rectangle visibleTilesRegion = new Rectangle();

private void updateVisibleTilesRegion (){
    // Define a ray that is a projection of the direction the camera is looking onto the 
    // tile plane (assuming it is a Z=0 plane).
    tmpRay.origin.set(camera.position.x, camera.position.y, 0f);
    tmpRay.direction.set(0f, 1f, 0f);

    //Find top and bottom
    Intersector.intersectRayPlane(tmpRay, camera.frustum.planes[4], tmpVec);
    float yTop = tmpVec.y;
    Intersector.intersectRayPlane(tmpRay, camera.frustum.planes[5], tmpVec);
    float yBottom = tmpVec.y;

    // Find left and right at the top of the screen by intersecting that line with the left 
    // and right planes
    tmpRay.origin.set(camera.position.x, yTop, 0f);
    tmpRay.direction.set(-1f, 0f, 0f);
    Intersector.intersectRayPlane(tmpRay, camera.frustum.planes[2], tmpVec);
    float xLeft = tmpVec.x;
    tmpRay.direction.set(1f, 0f, 0f);
    Intersector.intersectRayPlane(tmpRay, camera.frustum.planes[3], tmpVec);
    float xRight = tmpVec.x;

    visibleTilesRegion.set(xLeft, yBottom, xRight - xLeft, yTop - yBottom);
}