Bryce 7 Pro render artifacts

judykerr3d_e8cf35e3dc

Has anyone seen this issue before? I am texturing a model in Bryce 7 Pro, and when rendering I'm seeing little black squares or triangles alongside some of the meshes, but only at certain viewing angles (see image renderartifacts_1). The problem only appears on the castle roofs, which all have the same picture texture, so I tried changing the texture to Bryce default grey, but the artifact still shows up, which I assume means it isn't a problem with the texture. Moving the camera right up to one of the roofs also shows a black triangle on or near the roof surface, close to the artifact (image renderartifacts_2). I checked the original model (made in Hexagon) to make sure there weren't any superfluous faces left lying around, and there weren't. The roofs were all done in quads in Hexagon, but I suspect that the Bryce import changes them to tris, and I'm wondering whether something might have gone wrong when they were imported. The lighting and sky settings make no difference to whether the artifacts appear or not, and neither does changing any render settings. The only thing that gets rid of them is changing the camera angle. They appear at the angle shown in the first image, and at the exact reverse angle from the other side of the castle, and they don't appear at any other angle, which makes me think it's some problem with the meshes. 

I've already textured and rendered the same model in Vue (D'Espirit) 10, using the same textures, without this problem showing up anywhere. Any suggestions would be much appreciated!

Horo

I've seen such in terrains but very rarely. Try to rotate the camera by 0.01° left or right.

judykerr3d_e8cf35e3dc

Horo said:

I've seen such in terrains but very rarely. Try to rotate the camera by 0.01° left or right.

Hi Horo, thanks for the response. 

I've tried your suggestion, but it doesn't make any detectable difference. I also just tried nudging the camera round by a degree at a time, and it actually takes a 35 degree turn one way of the other turn to get rid of them completely. So that's a 70-degree window that the render looks bad in, from two sides of the model. If I was just doing this for fun I'd live with it, but I was planning to upload this model as a freebie, and even if it's free I wouldn't want to put it out with a problem like this. 

What I think I'll do is re-export the the roof meshes from Hexagon, maybe in a different format, and see if that helps. 

Horo

Thank you for reporting back. So it's not the camera, maybe the model. Exporting and re-importing may help. If you use the 3DS format, the mesh doesn't get smoothed, if you use the OBJ format, the mesh gets smoothed. If I remember correctly that's how it works with Wings3D.

Slepalex

judykerr3d_e8cf35e3dc said:

Has anyone seen this issue before? I am texturing a model in Bryce 7 Pro, and when rendering I'm seeing little black squares or triangles alongside some of the meshes, but only at certain viewing angles (see image renderartifacts_1). The problem only appears on the castle roofs, which all have the same picture texture, so I tried changing the texture to Bryce default grey, but the artifact still shows up, which I assume means it isn't a problem with the texture. Moving the camera right up to one of the roofs also shows a black triangle on or near the roof surface, close to the artifact (image renderartifacts_2). I checked the original model (made in Hexagon) to make sure there weren't any superfluous faces left lying around, and there weren't. The roofs were all done in quads in Hexagon, but I suspect that the Bryce import changes them to tris, and I'm wondering whether something might have gone wrong when they were imported. The lighting and sky settings make no difference to whether the artifacts appear or not, and neither does changing any render settings. The only thing that gets rid of them is changing the camera angle. They appear at the angle shown in the first image, and at the exact reverse angle from the other side of the castle, and they don't appear at any other angle, which makes me think it's some problem with the meshes. 

I've already textured and rendered the same model in Vue (D'Espirit) 10, using the same textures, without this problem showing up anywhere. Any suggestions would be much appreciated!

There is an egg object in the preset file. There is also such a dark triangle, which is visible at some angle.
All models are made up of triangles. Regular polygons in third-party programs are quadrangles, which actually consist of two triangles lying in the same plane. That is, the normals to these triangles are parallel, directed in the same direction and the angle between them is 0. Usually, only polygons are displayed in simulation programs, which can consist of two or more triangles. The normals in them are not always parallel. From a modeling point of view, this is wrong.
Sometimes when modeling or exporting a model to some format (OBJ, 3ds, etc.) and then importing it into another program, two adjacent normals of the same polygon are turned in opposite directions. Then the shader stumbles on such a triangle and such an artifact appears. This is a modeling or export / import error.
If all normals are turned in the opposite direction and such a surface in Bryce turns out to be just black, then the function of shader smoothing of the surface helps. You need to go to the editor by the "E" icon (edit) and click the "smooth" button.

judykerr3d_e8cf35e3dc

Slepalex said:

judykerr3d_e8cf35e3dc said:

 

There is an egg object in the preset file. There is also such a dark triangle, which is visible at some angle.
All models are made up of triangles. Regular polygons in third-party programs are quadrangles, which actually consist of two triangles lying in the same plane. That is, the normals to these triangles are parallel, directed in the same direction and the angle between them is 0. Usually, only polygons are displayed in simulation programs, which can consist of two or more triangles. The normals in them are not always parallel. From a modeling point of view, this is wrong.
Sometimes when modeling or exporting a model to some format (OBJ, 3ds, etc.) and then importing it into another program, two adjacent normals of the same polygon are turned in opposite directions. Then the shader stumbles on such a triangle and such an artifact appears. This is a modeling or export / import error.
If all normals are turned in the opposite direction and such a surface in Bryce turns out to be just black, then the function of shader smoothing of the surface helps. You need to go to the editor by the "E" icon (edit) and click the "smooth" button.

Thanks Slepalex, but I already tried manually smoothing all the roof meshes in Bryce 7 Pro after I noticed the problem, and it doesn't make any difference. 

I've also tried re-exporting the model from Hexagon as a 3DS and a DXF, but the artifacts still appear in the Bryce 7 render. What I have discovered, though, is that they don't appear at all in Bryce 5 (see image Bryce5test).  I've imported the model into B5 as a 3DS and an OBJ, and neither show any render artifacts. Unfortunately B5 is leaving out random parts of the model here and there (not the roofs), which might just be down to its size. Not sure it's worth carrying on, as uploading the model just for Bryce 5 is a bit of a waste of time. Maybe if we ever get a new version of Bryce, I'll try it in that!

Rashad Carter

You will need to triangulate the mesh in Hexagon before you export it and import it into Bryce. This triangulation step is the only way to be certain that the triangles end up rendering in Bryce with the vertices aligned as Hexagon intended them to be. I'm pretty certain that will work. All the best!.

judykerr3d_e8cf35e3dc

Rashad Carter said:

You will need to triangulate the mesh in Hexagon before you export it and import it into Bryce. This triangulation step is the only way to be certain that the triangles end up rendering in Bryce with the vertices aligned as Hexagon intended them to be. I'm pretty certain that will work. All the best!.

Hi Rashad, thanks for that! This evening acting on your suggestion I tried using the 'Triangulate non-planar facets' utility on one of the roofs, then re-exported it as an OBJ and imported it into Bryce7. That HAS made a difference - you can see in the image "NewRoof" that there is no black square sticking out of the roof at front right now. But there is still a little black triangle seemingly floating above the tiles in the close-up picture. I don't know of any other way to convert quads to tris in Hexagon apart from using 'Triangulate non-planar facets'. Was that what you had in mind? 

judykerr3d_e8cf35e3dc

UPDATE

If anyone is interested, I've stumbled upon a fix for this. In Hexagon, I changed the UV mapping for the tower roofs from cylindrical to planar projection, and, hooray, the little black squares and triangles were gone from the Bryce render. The UV change was applied to the original roof meshes that I hadn't triangulated, so it looks as if it wasn't a problem with the mesh itself. Interestingly, I could see the edges of the quads in Bryce when I selected the meshes, so it seems they were not changed to tris on import, unless the display is not showing the true structure. I thought from the beginning of this that the blue tile texture was to blame as it's a very poor one (but the only one I have of the actual tiles), but I tried putting the stone texture I used for the walls, which is much better quality, on one roof using cylindrical projection and I got the same issue. When I changed the mapping to planar, the problem went away. I have absolutely no idea why this should be. The cylindrical projection for the tiles did make them look a little neater than the planar projection does, but at least the model now renders quite well as long as you don't try close-ups. 

mindsong

judykerr3d_e8cf35e3dc said:

UPDATE

If anyone is interested, I've stumbled upon a fix for this. In Hexagon, I changed the UV mapping for the tower roofs from cylindrical to planar projection, and, hooray, the little black squares and triangles were gone from the Bryce render. The UV change was applied to the original roof meshes that I hadn't triangulated, so it looks as if it wasn't a problem with the mesh itself. Interestingly, I could see the edges of the quads in Bryce when I selected the meshes, so it seems they were not changed to tris on import, unless the display is not showing the true structure. I thought from the beginning of this that the blue tile texture was to blame as it's a very poor one (but the only one I have of the actual tiles), but I tried putting the stone texture I used for the walls, which is much better quality, on one roof using cylindrical projection and I got the same issue. When I changed the mapping to planar, the problem went away. I have absolutely no idea why this should be. The cylindrical projection for the tiles did make them look a little neater than the planar projection does, but at least the model now renders quite well as long as you don't try close-ups. 

Thanks for that update - I wouldn't have expected a fix in that direction, so it's great that you shared that!

cheers,

--ms