Image-refraction at bottom of a swimming pool fails.

[Anonymous]

Greetings,

Please refer to MAX attachment and required PNG image file. Attempting to render an image at the bottom of a swimming pool. 

Can’t get the expected coverage that works out using geometry. The projected pattern should not be hitting the sides of the pool as it does when the pool is empty (shown here (refer to hidden layer ‘AV-REF-GEOMETRY”)).

When “AV-POOL-WATER-solid” layer (with refractive material applied) is un-hidden it appears to reduce image brightness but coverage is unaffected.

Using Max2014, but problem persists in Max2018 also.

Thank you.

Stephen Scott

[hagen.deloss]

Hello @Anonymous,

Thanks for posting your question in the forums, and sorry for the delayed response!

I have been looking at your scene file, and want to make sure I clearly understand the issue you are encountering.

Looks like you have a glass material set up on your water shape, and a light pointing directly down into the pool that has an image projection mapped to it.

It seems as though the light is what is causing a lot of the abnormal and spotty depiction of the image at the bottom, coupled with a high reflectance settings on a material that doesn't reflect like water causes the light to reflect the below image in abnormal ways. 

What renderer are you currently using for the attached renders? Also, have you tried using the Autodesk water premade material in Mental ray?Here is a little test i rendered, i dunno if its the style of what you are going for though.

I hope this helped, I would love to further discuss and troubleshoot this setup you have! Talk to you soon

Please select the Accept as Solution button if my post solves your issue or answers your question.

[Anonymous]

Hello,

Thanks very much for your response.

I am using MentalRay in 2014. Tried the 'water' material and got a similar result. This is a real world projection situation we are trying to predict. The pool would be close to a perfect waveless water surface. The expected 'main-image' at the bottom of the pool (ignoring reflections) should not hit the pool walls.

Thanks again for any insights you can offer.

Stephen Scott

[Anonymous]

Greetings,
I posted a reply on the forum.

[CAMedeck]

I think I understand where this is going now...

You want the water object to actually bend the path of the light being projected from your light source to emulate what would really happen if a light was projecting an image onto the bottom of a pool in the real world.  

What you need is Caustics.  Without it, Max will not reflect or refract light.  It can do it to rays when rendering through glass or water, but the actual light is not bent, only the picture we see.  Enabling Caustics will tell Max to affect the path of the light energy.  And take a lot longer to render.  And there's a lot of fiddling with settings to make it look just right.  

Google 3ds Max Caustics, and you'll find some tutorials and explanations of how it all works.

[Anonymous]

That's exactly what I want. I need to show the result of refraction (bent light path) and how the coverage is reduced as compared to the absence of water. I will try 'caustics'.

Thanks.

[rendermaster]

I have done one tutorial for Mental Ray Caustics posted at Evermotion. Check this out: https://evermotion.org/tutorials/show/7972/caustics-in-mental-ray-tutorial

here is the sample image.

[hagen.deloss]

Hi @Anonymous

I wanted to check back and see if you looked into using caustics for this render like @CAMedeck and @rendermaster suggested. 

If and when you do, it would be super helpful if you could add a post with how you decide to proceed, and your results. That way other Community members can benefit from your process

Please select the Accept as Solution button if my post solves your issue or answers your question.

[Anonymous]

Caustics helps. I can see the effect of the refraction. Problem is the image gets 'absorbed' by the 'water-solid' so there is no image on the bottom of the pool. I'm sure my settings are wrong but have no idea which ones to adjust.

[Anonymous]

Using "Caustics" makes a difference. But, the image quality I get upon rendering, though generally correct, is lacking in quality no doubt dependent on other settings I have no idea about.

[hagen.deloss]

Hello @Anonymous

Its great to hear that Caustics is helping out!

I think there are a few things factoring in to the darkness of your scene. When the light hits your water surface, its trying to bounce the lights off six different sides, instead of just one. I would recreate your water object to be a single plane, covering only the top of the swimming pool. 

I would also suggest changing your light type to an area light, as your current top down directional light may be casting some harsh, confusing shadows onto the mesh below as well.

In regard to caustics, I actually found this really neat walkthrough on youtube that I would suggest following along with (I'm going to). It doesn't have any sound, but it creates a pretty neat effect that could help teach some caustic settings in a hands on way. 

Oh, and in reply to render settings, this video also goes over some global illumination settings and production render stuff, but that really depends on your specific scene, here is some more general information about that. 

I hope this information helps! Talk to you soon

Please select the Accept as Solution button if my post solves your issue or answers your question.

[Anonymous]

Hello,

I used your recommendation of a plane just for the water's surface. First image is 'empty' pool showing over-projection on the sides of the pool. Second image is with water-plane and caustics rendered showing how refraction affects the coverage (reduced) at the bottom of the pool. This is what I would have expected.

Thank you.

[hagen.deloss]

Hello @Anonymous,

I got the same results. I suggest that you also change your lighting to a omni light, as the harsh directional light isn't helping the shadows bouncing off the glass materials. 

I took some time and did some tests with the scene you provided to illustrate why I suggest using the Autodesk Water Material over a glass material, this, among a few others, is the reason why you are getting such a dark render. I have also attached the scene with the changes I made to the scene, I hope you don't mind!

As you can see, I added a noise modifier onto a dense, single plane mesh to get the watery effect, I got the technique from the video I linked above. I took off the image you linked to your light, as it was creating visual noise, I added it back in as a texture map to the bottom of the pool in this next render.

I would suggest fully unwrapping your swimming pool and adding a full tile texture, but that depends on how realistic and detailed you want this shot to be.

There are a lot of connected parts to this, so please clarify if I misunderstood your intent with this project! And also please let me know if you have further questions about any of this! 

Please select the Accept as Solution button if my post solves your issue or answers your question.

[Anonymous]

Hello,

The object of this exercise is to visualize the real-world effect of refraction (caused by the water in an indoor pool) on an image projected from above through the water to the pool bottom surface. A projector light is used so that I can emulate a specific physical projected image size (based on available lenses). When this setup is installed and in use the pool surface will be near to a perfect flat plane (no ripples due to pool operations/filters etc.) and the water should be almost perfectly clear. Room lighting would also be minimal.

Thanks for your help.

Stephen

[hagen.deloss · Accepted solution]

@Anonymous

Thanks for the clarifications!

I would suggest selecting the bottom of the pool deck mesh and detaching it.

I would then go into the  light settings and click on the exclude button. That will bring up a list of all the objects within the scene. You can exclude the outside parts of the pool, that way the projection will only project onto the bottom of the scene! Here is where the exclude button is, and what the pop up looks like.

I hope this helps! 

Please select the Accept as Solution button if my post solves your issue or answers your question.

[Anonymous]

Hello H.D,

Can you send me a copy of your Max file so that I can see your settings, please? Following your recommendations I get roughly the same as you do (minus the ripple which I definitely don't want) except the blue-grid rendering in yours seems much brighter.

Thanks,

Stephen Scott

[hagen.deloss]

Hello @Anonymous

I have attached the test scene to this message, but I encourage you to try and recreate the effect on your own using the exclude feature on your light 😄

If my previous comments have helped you, make sure to mark the ones with relevant information as the solution, that way the rest of the community can benefit!

[Anonymous]

Thanks again for your help hagen.deloss . I was been away from this project so unable to test your file until now.

I have been working in Max2014 since I have a few plugins that only work there. Though I have Max2018 I am not using it and I am not getting the expected results when rendering your file. Is there a particular renderer that I need to use from those available in Max2018?

Thanks,

Stephen