3D Modeling Artifacts / Flow Check Reflection Map Tutorial


Hello everyone, We received a lot of questions on this colorful flow check reflection map you see over here. This is something originally borrowed from NURBS 3D modeling tools, It’s basically a striped reflection map that can show us the surface quality and how it will reflect in an environment. We will quickly see how it’s used. But, please hold on until we go through some quick basics and different types of 3d modeling artifacts. To state it perfectly clear beforehand though, you don’t need to use this reflection map on everything you model, and we don’t recommend using it for most of your work, in fact it’s only used in specific situations. Let us start by seeing how the flow check map looks like on a smooth surface. By adding some artifacts which is nothing more than a fancy word for bumps, dents and overall surface irregularities by the way, you get an idea about the general use of this map, unfortunately though, most 3D modeling artifacts are not so straightforward and are oftentimes unavoidable. Please take look at these surfaces in contrast to the ones next to them. The distortion is quite visible, but what’s the cause of it? Adding even one single edge can make all the difference! This is because a new edge is changing the averaging of the new mesh points and the topology of the subdivided mesh. The more a surface is curved; the more pronounced are artifacts caused by subdividing triangles and N-gons will be. To briefly explain why this happens in subdivision, take a look at this example:
This is how a single quad is subdivided. If you make a cut, then all of a sudden you have a new topology and new vertices will shift position towards it. And this is how different topology can produce different subdivisions. different subdivision algorithms, or different software implementation rules, could give slightly different results especially around corners. Catmul Clark subdivision is really straight forward though. This is the formula for how subdivision works and how new faces, edges and vertices positions are calculated. If you have time we highly recommend you watch these two lectures which would give you a deeper understanding of how things work under the hood and you will no longer be impressed by the word topology! Perhaps this would be a good time to mention that bumps, dents, and using triangles or N-Gons for subdivision is not something to be always frowned upon, in many instances, it can even help increase the quality of your surface and make it appear more natural. For example, if you are modeling this ship hull, you probably would not need to be very careful with small or even big bumps, as you can see in the render, a little bump and dent here in there did surprisingly help the overall look and feel of the ship. So far, all the artifacts we have gone though can be easily detected with a standard material and does not require the use of a flowcheck map,. Once we move to the really subtle effects of modeling artifacts though we start to appreciate a reflection test map much more. These effects can only be observed when the surface is very reflective and is put in an environment that have distinct features. But what do we exactly mean by that? Using a standard shader, this car 3D model looks in fairly good shape, the edge loops look well distributed and it seems of a high quality. But surprisingly when rendering it in a studio environment, you start getting these artifacts and reflection distortions. Polygon modeling is inherently limited and unable to imitate the same level of control and analysis we have in a NURBS software. But using this simple flow check map and viewing it directly in the viewport when modeling in polygons could help us know what to expect at render time. With polygons there is not much you can do to improve the quality of surface reflections but you can at least focus on getting the bigger surfaces correctly. To read more about this subject I recommend reading “car modeling in polygons article”, linked in the description below. as you will read in the article, improving your 3D polygon models can be summed up by better 3D modeling practices which deserve a complete video which will be covered in detail in a future car modeling tutorial we are in the process of making at the moment. To reiterate what we said in the beginning of this video, if you do not need to go this far in terms of quality, don’t bother with any striped environment maps, if you are doing an outdoor skydome exterior render and you don’t think anyone will notice some irregularities in the reflections. Please try to finish your 3d modeling as quickly as possible and as accurately as you need to and don’t bother with any flow check maps. To give you an example of the difference between using a flow check reflection map and not using one. Here you can see how the reflections on the doors are broken up. allso here on the hood and around some details,, when I rendered an animation for it, the distortions were more visible as the reflection streaks passed the model, if I had used the flow check map prior in modeling, I could at least anticipate the problems I might have ahead of time Although this newer car has a much more challenging pattern to emulate, I managed to get a somewhat of a resemblance of the real car reflections. To Sum up. 3D modeling artifacts can vary in degree and reasons, better polygon 3D modeling practices can help alleviate some of these issues to some extent. Using a flow check map like the one we have seen will enable you to predict how a surface will react in an environment. To download this HDRI, you can access our gumroad page, and download it from there. How to view this reflection map in your viewport: To view it in max: -Change your renderer to Nvidia Mental Ray Select the flowcheck map HDRI as an environment background. Select Views, Viewport Background and select environment background. Now assign an arch and design mental ray, and select a chrome template and assign that material. Select Views again, show materials in viewport as, realistic materials with maps One disclaimer, this is the easiest way I have found to work to view an environment reflection in the viewport, autodesk might change the settings or the position of the buttons later on. To view it in Maya: Apply a phong shader with a black diffuse color. Use an environment sphere in the reflection color. Select the flow check HDRI. Select shading, hardware texturing. And you are done! We do understand that we might have packed a lot of material in this video which needs more examples to get some points across, if you have any feedback or things you would like us to expand upon, please let us know in the comments section and we will try our best to include them in future videos. Thank you for watching,

11 Replies to “3D Modeling Artifacts / Flow Check Reflection Map Tutorial

  1. i remember your work on pdf that i got from 3dm3.com several years ago. You are indeed very talented 3d artist.

  2. Thank you for the tutorial! In the beginning of the video the viewport background is black and at the same time the objects reflecting the HDRI map. But when you are showing how to do that the background also is HDRI map and this is tiresome for eyes when you are working. How to make viewport background only solid color but at the same time reflecting on the model?

  3. Awesome process of modeling and material ! Thanks a lot for this. I have a little question though, if you're familiar to Maya and 3DSMax, what is the best option for car modelling ? what is lacking in each of them and what is better ?

  4. 7:46 same for 3ds max. Diffuse color to black. Put .hdr to reflaction map with Spherical Env. Mapping. https://i.imgur.com/tIln9VL.jpg. And use Realistic materials with maps. https://i.imgur.com/xThSPtV.jpg

  5. Nice to see such high level in polygonal modeling. I can see that the side has been improved a lot. What about the roof? Is that the best one can achieve with polygonal or wasn't it your intent?

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