Baking pixel-perfect maps is extremely inaccurate #74823

New Issue

Vyacheslav Kobozev · 2020-03-16T19:24:42+01:00

2020-03-16 19:24:42 +01:00

System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: GeForce GTX 660 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.59

Blender Version
Broken: version: 2.83 (sub 9), branch: master, commit date: 2020-03-15 22:43, hash: f06a6e92bc

Short description of error

untitled1.blend
2020-03-16_21-22-35.mp4

Islands are not null sized. They aligned to pixel centers.
And i still can`t bake em all. Try to bake with this file.
Such baking need fpr pixel-art and poly-art baking.

**System Information** Operating system: Windows-7-6.1.7601-SP1 64 Bits Graphics card: GeForce GTX 660 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.59 **Blender Version** Broken: version: 2.83 (sub 9), branch: master, commit date: 2020-03-15 22:43, hash: `f06a6e92bc` **Short description of error** ![32712616.jpg](https://archive.blender.org/developer/F8410667/32712616.jpg) [untitled1.blend](https://archive.blender.org/developer/F8410669/untitled1.blend) [2020-03-16_21-22-35.mp4](https://archive.blender.org/developer/F8410678/2020-03-16_21-22-35.mp4) Islands are not null sized. They aligned to pixel centers. And i still can`t bake em all. Try to bake with this file. Such baking need fpr pixel-art and poly-art baking.

Vyacheslav Kobozev commented

2020-03-16 19:24:42 +01:00

Added subscriber: @Vyach

Szymon Ulatowski commented

2020-03-17 04:23:02 +01:00

Added subscriber: @szulat

Szymon Ulatowski commented

2020-03-17 04:23:02 +01:00

It seems that this is how it is designed.

The rule is, a given pixel only belongs to one polygon. Very tiny polygons (less than 1 pixel) are completely ignored by rasterization, unless they cross pixel boundaries. This way the produced pixels don't overlap, but they can still fill the texture without holes, assuming the correct mesh topology. Tiny islands, on the other hand, are only visible "by chance". Perhaps the algorithm could be extended to treat island edges differently: they would be always fully rasterized, ignoring the usual polygon rules? Not sure if this is the correct way. More complex definitely.

Changing

my0=ceil(minv[1])

to

my0=floor(minv[1]);

in zbuf_add_to_span() and removing

sn1++;

in zspan_scanconvert() nearly "fixes" the problem (and of course breaks something else, because it is not selective).

Anyway, you don't absolutely need it to achieve the effect. Instead of producing exact pixel values directly, bake to bigger texture (so your bake polygons are well above 1 pixel in size), and then produce your pixel texture from this bigger bitmap.

**It seems that this is how it is designed.** The rule is, a given pixel only belongs to one polygon. Very tiny polygons (less than 1 pixel) are completely ignored by rasterization, unless they cross pixel boundaries. This way the produced pixels don't overlap, but they can still fill the texture without holes, assuming the correct mesh topology. Tiny islands, on the other hand, are only visible "by chance". **Perhaps the algorithm could be extended to treat island edges differently: they would be always fully rasterized, ignoring the usual polygon rules?** Not sure if this is the correct way. More complex definitely. Changing ``` my0=ceil(minv[1]) ``` to ``` my0=floor(minv[1]); ``` in zbuf_add_to_span() and removing ``` sn1++; ``` in zspan_scanconvert() nearly "fixes" the problem (and of course breaks something else, because it is not selective). Anyway, you don't absolutely need it to achieve the effect. Instead of producing exact pixel values directly, bake to bigger texture (so your bake polygons are well above 1 pixel in size), and then produce your pixel texture from this bigger bitmap.

Vyacheslav Kobozev commented

2020-03-17 19:55:37 +01:00

@szulat sadly, even relatively big island, that crossing three pixel boundaries, still not give a chance to bake it.
okay, i will try to get pixel texture from bigger result? but I am not sure, result will be proper and solid.

@szulat sadly, even relatively big island, that crossing three pixel boundaries, still not give a chance to bake it. okay, i will try to get pixel texture from bigger result? but I am not sure, result will be proper and solid.

Germano Cavalcante commented

2020-03-24 14:23:36 +01:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-03-24 14:23:36 +01:00

I tested the file and the behavior seemed to be as expected.
Some triangles are not overlapping the middle of the pixel, so the resulting color is Alpha.
This is the expected when you decrease the resolution of a texture.
https://en.wikipedia.org/wiki/Texture_filtering

Did I misunderstand the problem?

I tested the file and the behavior seemed to be as expected. Some triangles are not overlapping the middle of the pixel, so the resulting color is Alpha. This is the expected when you decrease the resolution of a texture. https://en.wikipedia.org/wiki/Texture_filtering Did I misunderstand the problem?

Germano Cavalcante commented

2020-03-25 19:04:55 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Vyacheslav Kobozev commented

2020-03-30 06:44:21 +02:00

@mano-wii
Oh, thanks!
So tris can be small but should cover the centers of pixels.
Yes, that solves the problem.
It is more like I misunderstood how it should work.

@mano-wii Oh, thanks! So tris can be small but should cover the centers of pixels. Yes, that solves the problem. It is more like I misunderstood how it should work. ![33550643.jpg](https://archive.blender.org/developer/F8436311/33550643.jpg)

Vyacheslav Kobozev commented

2020-03-30 06:49:37 +02:00

Changed status from 'Needs User Info' to: 'Resolved'

Vyacheslav Kobozev closed this issue

2020-03-30 06:49:37 +02:00

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Baking pixel-perfect maps is extremely inaccurate #74823