Two-Tone Tree

Summer is turning into autumn at alarming speed in my neck of the wood. As I was strolling through the city the other day, trying to imbibe the feeling, I couldn’t help notice how most of the trees were not assuming their autumn shades in a uniform way. Rather, it seemed the chlorophyle was first deserting the tip of their branches, then receding towards the trunk, leaving behind it a gradient of yellows and crimsons to green. These photos are pretty bad, but you get the idea.

This (obviously) got me thinking about how one would go about recreating this effect in Max. Assigning different mat IDs to the leaves would not work because the only practical way to do it would be to assign them randomly. And what I saw there was definitely not random.

I remembered the issue had been addressed briefly in the great “realistic foliage” thread at ronenbekerman (these kinds of tip-to-trunk gradients are not just seen in autumn trees). The question was not answered, but someone did mention soft-vertex-selections – and that got me thinking: One way to do this would be to turn a soft-selection of vertices into a vertex colour and use this as a mask between two materials.

In the event, it was even simpler. The following vertex colour mask was generated by painting the tips of a random tree black using a very large brush (to generate a nice, soft gradient).

The vertex colour map was then used as a mask to blend between two 2sided materials – yellow and green. For even more realism, one could create random variations within the yellow and the green group (all leaves here have random mat-IDs).

This was the result:

Now I wonder how one would create a three-tone gradient: red-yellow-green. Any idea much welcome.

18 Comments

  1. BBB3VIZ wrote:

    Prakash: I don’t think that would work, or it would be extremely difficult to do well. By going the 2D route, you would lose the sense of depth (leaves changing colours the further away from the trunk they are). I suspect such an image would lack a little something but am happy to be proven wrong.

  2. Prakash wrote:

    First Render your tree in 3D with a single difuse texture. and then take to phop. Photoshop is the best way to get the gradation in color.. just try using brush tools with colors of ur choice with a suitable blend mode .!! you can also use saturation/desaturation tools..the final result should be the same what is being given in this tutorial !! . Just KISS …Keep It Simple Silly ..:)

  3. benoit-basset wrote:

    Magnifiques photographies, l’automne sublimé.

  4. Robson wrote:

    You can also use the falloff map to control the changing between the colors of the leaves . Just change the falloff type to “distance blend” and the falloff direction to “object” .Set the object to be your trunk and set the far distance as needed .

  5. BBB3VIZ wrote:

    Thanks for all the tips.

    I like the idea of using the VrayDistanceTex with invisible objects, but I originally wanted a slightly leaner solution that would allow me to save the material on a proxy easily. I’m not sure how this solution would work with proxies given the invisible objects, or if it could be replicated on lots of trees. Got to test it.

    I like the idea of the gradient map using the vertex colour as input. Again, it is something I intend to play with as soon as I get the time.

    Jacinto: Yes, vertex painting on a 2m-poly beast is not that fun. You got to arm yourself with patience. Still, it is vastly faster than trying to do this with soft-selection, which was the first approach I tried but proved to be completely unworkable for that reason.

  6. Danio wrote:

    Following up on what Mark suggested I did some tests last night. I posted to my blog about it here:
    http://carpitecture.blogspot.com/2012/10/vraydistancetex.html

    and if you just want the image results they are here:
    http://2.bp.blogspot.com/-7usi7MmVISw/UHm7aS4hS2I/AAAAAAAAAQw/Kod8TpSK6Ps/s1600/DistanceTrial4.jpg

    Here:
    http://1.bp.blogspot.com/-yr4udhTQAAE/UHm7nT2fc0I/AAAAAAAAAQ4/X8bZrXYSHeY/s1600/DistanceTrial3.jpg

    and the Mat setup here:
    http://1.bp.blogspot.com/-fILEVS4ORuk/UHm8ks4efJI/AAAAAAAAARI/uv35mZ6rDIs/s1600/SlateMatTwoTone.jpg

    Awesome idea Mark. This is a super fast setup. Just having some trouble controlling the falloff from the VRayDistanceTex object.

    Also when you move your ‘objects’ (spheres, whatever) things get a little laggy. I don’t know of a good work around for this but everything is fast once you’ve moved them into place. I wonder if you could group your objects in a proxy….

  7. Deshu Diosh wrote:

    Hello! Here is the way, which I’d use. It uses painting 2 separate vetrexpaints, and using them as masks – pretty similar to technique you presented. It gives big control over blending. Hope, you’ll find it usefull.

    1. final result: http://i1197.photobucket.com/albums/aa425/deshu1/vertexpaint%20blend%20tut/1_zps24bbe175.png
    2. first vertex paint: http://i1197.photobucket.com/albums/aa425/deshu1/vertexpaint%20blend%20tut/2_zpsb1fa5ddb.png
    3. second vertex paint: http://i1197.photobucket.com/albums/aa425/deshu1/vertexpaint%20blend%20tut/3_zps4419d471.png
    4. material: http://i1197.photobucket.com/albums/aa425/deshu1/vertexpaint%20blend%20tut/4_zps7c554e60.png

    You can easily apply this to textures, instead of materials.

    P.s. thank you for this blog. Always waiting for next post. Beautiful renders, oh lord!

  8. I have used the same vertex paint procedure to paint horizontal two tone surfaces like in grass, pavements etc. But I never thought about doing it in trees. Great idea. Isnt it slow while painting?

    Best r,

  9. gjpetch wrote:

    To get a more complex gradient use a gradient ramp map with type set to “mapped”, and put a vertex color map into it’s source map slot.

  10. Mark Whelan wrote:

    If you are using Vray, another way to do this, with a little more control would be to use the VrayDistanceTexture and a few spheres placed near the areas you want colored, and use that as a color mask. This way its easier just to move clumps of colour by moving the spheres.

  11. jorge wrote:

    Use a gradient ramp in mapped mode using a vertexcolor as mapping driver. Tested in a sphere and worked quite well. Awesome blog, by the way.

    Cheers,

    Jorge

  12. Vhector wrote:

    You have differnt kinds and ways of coloration (wheater, daylength, location and type). I’m trying to achieve that by diffent type off falloffs through object based light based and mix curvation.

    Leaf fall and leaf discoloration is a process that annual returns and now is going to be up to date. The main factor that influences this process is undoubtedly the day length, this is the most constant over the years, but the temperature plays a role. Trees (at least most) lose their leaves to protect themselves against dehydration. Trees absorb with their roots in water containing dissolved nutrients. Through the stomata of the leaf evaporate the greater part of this water again.
    In winter the soil temperature dropped so far that the roots are no longer able to absorb water. Would the evaporation through the leaves would just keep the tree from drying out. Therefore, most (deciduous) trees shed their leaves. There are exceptions, such as holly and rhododendron, these have sturdy leaves with a leathery surface and there are few stomata.

    Journal Discoloration

    Journal Discoloration comes about because the chloroplasts are broken. In addition, there are also other chloroplasts (color) substances present in the leaf. These substances are visible after the chlorophyll grain is broken. These substances shall ensure that a tree typical autumn color. Red coloration comes from anthocyanin, yellowing from the substance xanthophyll and carotene produces an orange color.

    Not all the trees discolor in the same manner. In some species the discoloration begins at the edge. For example, a horse, some leaves have a mosaic discoloration example in Maple. Other types of leaves colors more evenly to a certain color. For example, Virginia creeper is bright red, a yellow and a hornbeam beech leaves get brown. Some are black, for example, the narrow leaves of a willow, but there are also trees that barely discolor example es.

    How the leaves fall over?

    The fact that the leaves fall from the tree is mainly driven by the wind and is not as some have thought. A storm in the summer the leaves neatly hanging on the tree, but an autumn walk through a forest where there is no wind you can see leaf drop. This is because a normally a tree leaf drop produces inhibitory hormone, called auxin. Due to the aforementioned influences autumn (daylength and temperature drop), the leaf fall inhibitory effect of auxin increasingly less. This is a separation layer in the petiole developed. This is done also under the influence of a hormone (abscinezuur). This creates a layer between the petiole and the branch (also called tear tissue called). The vascular tissues remain intact as long as possible (see picture above), but eventually releasing the blade anyway because this crack tissue slowly but surely perish, and then the leaf falls down.

    For example, when in the summer a branch of a tree is torn then these leaves are dry, because they have no food and water more. But the tree has not been able to make the tear layer and thereby keep the dried leaves just sitting on the broken branch.

  13. Federico wrote:

    i use advance painter on the trees for this effect, but this way is much better! thanks

  14. clark aranda wrote:

    I have not idea , but it is a amazing solution :)

  15. miki3D wrote:

    That is a very nice solution to having very realistic looking trees!

    I think the solution to having three gradients could come from the same technique, by simply nesting a new blend material in one of the parent blending slots, and using a different mask to show the two sub gradients.

    I hope I made sense ;)

  16. Patrick wrote:

    Thought I’d have a quick stab at this. I placed the vertex colour map into two output maps with seperate curves to define where the gradient appears.
    http://reformstudios.com/images/threetone.jpg
    Is that what you were looking for?

  17. Danio wrote:

    Wow, super cool idea. I was just wondering this week how one might achieve this in Max as all the trees around me are now turning red at the top thanks to the cold night sky so it was awesome to see your post.

    A slick solution would be if GrowFX had a ‘clumping’ option like Forest Pro it seems like. It could clump mat IDs.

    Dan

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