Jagged shading of surfaces


I’m new to the forum but have used it quite a bit when trying to figure stuff out.
I now have a real issue. I have recently changed my graphics card and now the shading of the surfaces have jagged edges. Is this SU or do you think it’s a hardware issue?


Is model located faraway from Origin?

Hi, Thanks for responding.
No the model is right next to it

Can you share the model so we can see if we can spot an issue? If it is larger than about 15MB you will need to upload it to a file sharing site and post a link here. Otherwise you can drag-n-drop it into a forum reply window as you did with your image.

Hopefully this will work

You have the camera as parallel projection, and then zoomed in far enough to see the model. In perspective the model ends up being tiny. It’s curious that you work in parallel projection, but you can fix the issue by switching to perspective, then zoom extents, and then switch back to parallel projection.

Oh okay,

I didn’t realise it made a difference, I’ll try what you’ve suggested and get back, thanks

Got it.

You are seeing an example of “z-fighting”, in which the graphics system is struggling to decide which of multiple objects should be in front of the other from the current point of view. The giveaway is that the effect flashes and shifts as you orbit the model because the graphics keeps changing its mind. As @colin observed, this is happening because you are working in parallel projection and the camera has gotten to be far away from the model. Having the camera so far away aggravates z-fighting because distances from camera to model are almost the same.

This camera positioning issue is a well-known problem with parallel projection, and is why the experts all recommend that you model in perspective projection and only change to parallel for final orthographic views if needed in your presentation documentation.

On other issues I noticed, you have a lot of reversed faces in the model that you should correct. Set monochrome mode so that textures don’t mask the situation and look for blue-gray faces that are exposed (I set a bright green for the back face color in the style to make reversed faces jump out).

You are also not using tags (formerly called layers) appropriately. All edges and faces should be untagged. Tags should be applied only to entire groups or components. Edges and faces inside a group or component don’t need tags because the whole group’s tag will control their visibility, and edges and faces in a single context (model, group, or component) will stick to each other and intersect regardless of what tag they use.

Purging the model reduced its file size from 25 to less than 4 MB.


Eventually sorted my model out. Thanks for the tips, I was aware that my drawing technique is not the best atm. So thanks also for the extra tips too, I’ve just started using sketchup again for real drawings as oposed to simple modeling so, this is an oldish model. I’m now building proper components and using tags in the right way, you are all definitely my go to resource from now on :+1: