Preface OK, so I wrote this some time ago when I originally intended to include a much higher spec LOD option #4 with the big 3 trees using hybrid models or full lightweight 3D LOD models, which is now no longer the case. But rather than delete this article I thought maybe some may still find it interesting or perhaps even useful. Will option #4 still be released ..... Um, as to when, if or what, I am unsure, ask me again in about 3 or 4 months time. ====================================================================
Standard 2D billboard LOD for trees simply uses a 2D flat image of a tree for all instances of that tree outside of the attached cells (controlled by U grids to load). Each LOD version of the tree will have 2 flat panels separated by 90 degrees of rotation and intersecting each other vertically about their center point, with each panel (double sided) showing the tree image, ie the tree billboard picture. This is very efficient and uses just 4 triangles per tree, by comparison my lightweight 3D LOD tree uses about 300 and in full model about 1700 (in original TS the full model was 3,692). The 5 base vanilla pines which were replaced by TS were substantially smaller in size and triangle count, they ranged from 207 to 1128 with an average around 500.
The 3D LOD used in TSE is a by product of my aim to make true "no pop" LOD, it is a light weight 3D tree, and reasonably close to the full model look but it is not a "no pop" LOD model. Its just a simplified copy as light as I dare make it, for TSE, since I wanted TSE to be as PC friendly as possible. For no pop LOD the mesh has to present an outline to the players view point,identical to the full model in every respect , trunk, branch and leaf, but within that outline you must greatly reduce the detail or the PC resources needed to run it would be impossible if the tree is used on mass.
From in game experience of running TS with the three largest trees using LOD-level-4 3D models at 80% reduction on the full models I now know that my initial target could have been closer to 90% and still had good looking LOD, but every tree is different, the 3 large trees in TS were very heavy to start with. For many trees an 80 or 90 % reduction would not be necessary and it would look horrible anyway which defeats the purpose of trying to make good looking LOD.
Making 3D mesh to be used in tree LOD for the big TS trees was an incredibly time intensive and painstaking process of disassembling the trees into workable pieces, then for each trunk,branch and leaf set reducing the triangle count down to what was necessary, then re UV-mapping the pieces and putting it all back together again. If done properly and the "outlines" are unchanged, the new tree will fit perfectly inside the original model, from the bottom of the trunk to the top of each leaf tip, a perfect match. So in game as you move towards the tree it just get bigger till it eventually shows more detail as the full model takes over, there is no "physical" pop. In practice there can be a small color difference as LOD lighting is not the same as full model, but its very close and the alpha setting on the LOD leaf texture needs to be set with this in mind.
Mesh tools like decimation can sometimes be used to kick start this triangle reduction process but its mostly a manual job as you need to "image" in your mind what each section of the mesh on screen will look like before you start cutting.
How Does 3D LOD Work, How Is It different to Normal LOD & What is "no pop" (1 comment)
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The author has locked this comment topic for the time beingPreface
OK, so I wrote this some time ago when I originally intended to include a much higher spec LOD option #4 with the big 3 trees using hybrid models or full lightweight 3D LOD models, which is now no longer the case. But rather than delete this article I thought maybe some may still find it interesting or perhaps even useful.
Will option #4 still be released ..... Um, as to when, if or what, I am unsure, ask me again in about 3 or 4 months time.
====================================================================
Standard 2D billboard LOD for trees simply uses a 2D flat image of a tree for all instances of that tree outside of the attached cells (controlled by U grids to load). Each LOD version of the tree will have 2 flat panels separated by 90 degrees of rotation and intersecting each other vertically about their center point, with each panel (double sided) showing the tree image, ie the tree billboard picture. This is very efficient and uses just 4 triangles per tree, by comparison my lightweight 3D LOD tree uses about 300 and in full model about 1700 (in original TS the full model was 3,692). The 5 base vanilla pines which were replaced by TS were substantially smaller in size and triangle count, they ranged from 207 to 1128 with an average around 500.
The 3D LOD used in TSE is a by product of my aim to make true "no pop" LOD, it is a light weight 3D tree, and reasonably close to the full model look but it is not a "no pop" LOD model. Its just a simplified copy as light as I dare make it, for TSE, since I wanted TSE to be as PC friendly as possible.
For no pop LOD the mesh has to present an outline to the players view point,identical to the full model in every respect , trunk, branch and leaf, but within that outline you must greatly reduce the detail or the PC resources needed to run it would be impossible if the tree is used on mass.
From in game experience of running TS with the three largest trees using LOD-level-4 3D models at 80% reduction on the full models I now know that my initial target could have been closer to 90% and still had good looking LOD, but every tree is different, the 3 large trees in TS were very heavy to start with. For many trees an 80 or 90 % reduction would not be necessary and it would look horrible anyway which defeats the purpose of trying to make good looking LOD.
Making 3D mesh to be used in tree LOD for the big TS trees was an incredibly time intensive and painstaking process of disassembling the trees into workable pieces, then for each trunk,branch and leaf set reducing the triangle count down to what was necessary, then re UV-mapping the pieces and putting it all back together again. If done properly and the "outlines" are unchanged, the new tree will fit perfectly inside the original model, from the bottom of the trunk to the top of each leaf tip, a perfect match. So in game as you move towards the tree it just get bigger till it eventually shows more detail as the full model takes over, there is no "physical" pop. In practice there can be a small color difference as LOD lighting is not the same as full model, but its very close and the alpha setting on the LOD leaf texture needs to be set with this in mind.
Mesh tools like decimation can sometimes be used to kick start this triangle reduction process but its mostly a manual job as you need to "image" in your mind what each section of the mesh on screen will look like before you start cutting.