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added 285 characters in body

edited May 21, 2024 at 18:23

I have an isometric scene in a custom engine where my world sim is 3D, but I'm rendering sprites. To depth sort, I follow the approach in this blog post. Basically: wrap each sprite in an AABB, then sort them by depth.

The condition it uses to test if one of the sprite's AABBs is behind another is:

if (b.minX < a.maxX && b.minY < a.maxY && b.minZ < a.maxZ) { // b is behind a }

however, this doesn't produce the result I would like in a few situations. Say I have two boxes, where one is intersecting the other:

// BoundingBox is {minX, maxX, minY, maxY, minZ, maxZ} BoundingBox spriteABounds{0, 7, 0, 32, 0, 78}; BoundingBox spriteBBounds{0, 32, 0, 32, 0, 78};

The desired behavior would be for sprite A to be behind sprite B, but the above condition considers both boxes to be behind eachother.

Another situation is when dealing with planes (note that the floor tile isn't graphically a plane, but should be treated as one in the world sim):

BoundingBox spriteABounds{0, 32, 0, 32, 78, 78}; BoundingBox spriteBBounds{32, 64, 0, 32, 0, 78};

The desired behavior would be for sprite A to be behind sprite B, but the above condition considers neither to be behind eachother.

Is there a way that I can set up the condition to handle these cases appropriately, or would I need to switch to a different approach? If the latter, what approach would be more appropriate?

The condition it uses to test if one of the sprite's AABBs is behind another is:

if (b.minX < a.maxX && b.minY < a.maxY && b.minZ < a.maxZ) { // b is behind a }

however, this doesn't produce the result I would like in a few situations. Say I have two boxes, where one is intersecting the other:

// BoundingBox is {minX, maxX, minY, maxY, minZ, maxZ} BoundingBox spriteABounds{0, 7, 0, 32, 0, 78}; BoundingBox spriteBBounds{0, 32, 0, 32, 0, 78};

The desired behavior would be for sprite A to be behind sprite B, but the above condition considers both boxes to be behind eachother.

Another situation is when dealing with planes:

BoundingBox spriteABounds{0, 32, 0, 32, 78, 78}; BoundingBox spriteBBounds{32, 64, 0, 32, 0, 78};

The desired behavior would be for sprite A to be behind sprite B, but the above condition considers neither to be behind eachother.

Is there a way that I can set up the condition to handle these cases appropriately, or would I need to switch to a different approach? If the latter, what approach would be more appropriate?

The condition it uses to test if one of the sprite's AABBs is behind another is:

if (b.minX < a.maxX && b.minY < a.maxY && b.minZ < a.maxZ) { // b is behind a }

however, this doesn't produce the result I would like in a few situations. Say I have two boxes, where one is intersecting the other:

// BoundingBox is {minX, maxX, minY, maxY, minZ, maxZ} BoundingBox spriteABounds{0, 7, 0, 32, 0, 78}; BoundingBox spriteBBounds{0, 32, 0, 32, 0, 78};

The desired behavior would be for sprite A to be behind sprite B, but the above condition considers both boxes to be behind eachother.

Another situation is when dealing with planes (note that the floor tile isn't graphically a plane, but should be treated as one in the world sim):

BoundingBox spriteABounds{0, 32, 0, 32, 78, 78}; BoundingBox spriteBBounds{32, 64, 0, 32, 0, 78};

The desired behavior would be for sprite A to be behind sprite B, but the above condition considers neither to be behind eachother.

Is there a way that I can set up the condition to handle these cases appropriately, or would I need to switch to a different approach? If the latter, what approach would be more appropriate?

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asked May 21, 2024 at 6:50

Archduke

How to check if an AABB is behind another AABB while isometric depth sorting?

The condition it uses to test if one of the sprite's AABBs is behind another is:

if (b.minX < a.maxX && b.minY < a.maxY && b.minZ < a.maxZ) { // b is behind a }

however, this doesn't produce the result I would like in a few situations. Say I have two boxes, where one is intersecting the other:

// BoundingBox is {minX, maxX, minY, maxY, minZ, maxZ} BoundingBox spriteABounds{0, 7, 0, 32, 0, 78}; BoundingBox spriteBBounds{0, 32, 0, 32, 0, 78};

The desired behavior would be for sprite A to be behind sprite B, but the above condition considers both boxes to be behind eachother.

Another situation is when dealing with planes:

BoundingBox spriteABounds{0, 32, 0, 32, 78, 78}; BoundingBox spriteBBounds{32, 64, 0, 32, 0, 78};

The desired behavior would be for sprite A to be behind sprite B, but the above condition considers neither to be behind eachother.

Is there a way that I can set up the condition to handle these cases appropriately, or would I need to switch to a different approach? If the latter, what approach would be more appropriate?