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How to draw some objects "always on top"?

7 posts in this topic

HI, I need some help. I have a simple 3d system where Im displaying the axes of an object. The problem is if the axes is inside the object I cant see them. So I would like to be able to draw them so they are always visible regardless where they are in the 3d space. Just as when you select an object in blender or 3ds, you will see the objects axes regarles where they are located in the object. anyone?

Just like this picture (taken from Blenders homepage,, you can see axes on the bears arm even if they are "inside" the arm

Im rendering in dx11.

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Using a D3D11_DEPTH_STENCIL_DESC with depth writes disabled does the trick. Something like this:

[source lang="cpp"]
ID3D11DepthStencilState* EnableAllDSS;

memset(&depthdesc, 0, sizeof(depthdesc));
depthdesc.DepthEnable = (BOOL) false;
depthdesc.DepthWriteMask = D3D11_DEPTH_WRITE_MASK_ZERO;
depthdesc.DepthFunc = D3D11_COMPARISON_NEVER;
depthdesc.StencilEnable = (BOOL) false;
HR(device->CreateDepthStencilState(&depthdesc, &EnableAllDSS));

Then just set EnableAllDDS as the depth stencil state when rendering the axis arrows and reset it when done rendering them.

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You could also output depth 0 from the pixel shader used for drawing the axes (assuming less-equal depth testing and that this is not considered a performance-critical code-path).

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But without depth testing, it won't draw the coordinate system properly if it is a 3D object (which it is on the Blender example) - it won't do depth testing even between individual pixels of the axes and if let's say the blue arrow is partially hidden behind the green arrow, it can be rendered in a wrong way.

Isn't Ashaman73's solution the only proper one in this thread?

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If the arrows need to depth-test with themselves, but not the rest of the scene, you should render them using their own depth buffer (or clear the buffer before rendering the arrows). Edited by eppo

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easiest way is just render Axis with no depth testing [img][/img]

(d3d render state ztest off [img][/img] just at drawins Axis and then turn it on [img][/img] )

It's so easy I see some wrong answer above [img][/img]

but you need self depth test? Am I right?

then you need mask like stencil and so many other way..

How about this?

draw Axis to other texture and compositing it [img][/img] It's very easy and simple [img][/img]

but you must draw 3 times but you can debug Axis and object so easily ..I never use stencil. and I think It's not necessary at all at over DX 9 [img][/img]

any other help plz let me know [img][/img]

Ah sorry you just need turn on off Z test that's all :) I confuse with others message

sorry I'm new here and I'm Korean Edited by GeniusPooh

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