Strange reflections...


(marcanth) #1

While trying to play a little with radiosity and envmap, I came to something unexpected… I am wondering if this is a bug in Blender or what… Please take a look at this link and tell me what can be possibly wrong… Sorry not to explain everything here, but I will soon learn how to put images, etc. here in the forum. I am learning Blender and would like to know what can I do to solve this…

http://www.geocities.com/marcanth2001/blender/mirrorerror.html

Thank you. All comments and sugestions are welcome! :slight_smile:

Andre


(ec2) #2

Is this what you want?

I think the issue was that Z on your empty wasn’t perpendicular to your sphere. I rotated it 180 degrees in top view.

http://home.rochester.rr.com/earnest/macarnath.jpg


(marcanth) #3

:frowning: Yes, this is exactly what I want… however, I just opened the file here and tried to change the “z” 180 degrees, as you mentioned, but I still got the same error… That is strange… Did you saved it and opened it again? What was the result? I would appreciate if you could send the new .blend file… What exactly do you mean with “perpendicuar to an object”? I am a Blender newbie, so sorry if I ask so many questions… Thanks for your reply. Now I wish I could do it again and would like the result to be correct just as you did. Top view, 180 degrees… Didn’t work here… Are you using Blender Publisher 2.25?


(ec2) #4

First I apologize. I used Blender 2.23. I tried it in BP 2.25, and made sure in top view the Z was pointing toward the camera, and It worked ‘correctly’. Try it out. (And you can ignore my perpendicular comment it doesn’t apply here).


(marcanth) #5

Thanks, ec2! It worked as you said. So, when we are doing reflections (not planar) should we consider as a “rule” always pointing the “z” towards the camera, so that the reflections will be correct? When I opened the file, I adjusted the “z” towards the camera and it rendered “correctly”. But there is one thing I would like you to help me… What is the difference between

In textures buttons, in the Ob: I put “Sphere” (in my case, as I did radiosity the name changed, which is ok, so I put the correct name) and in materials button, on those green buttons I put “Object” and in that field next to it, I put the name of the Empty, which in my case it is “Empty”.

Now, which is the difference in doing the above to the following method:

In textures buttons, in the Ob: put “Empty” and in materials button remove the “Empty” and change the “Object” to “Refl” and render it again.

So, what is the difference between both methods, and which would be correct to make mirrors? If you open my file, you will see the first adjustment, but if you change the settings to the second and render it, you will see something wierd… This is something I would like to know. And if you save it, open it again and render, the result will be even different from the one just before you changed and saved. Does this happen with your Blender version?

Thanks,
Andre


(ec2) #6

No problem. I’m not sure that should be the rule per say. I got different results in 2.23 and 2.25. Plus I rarely use Empties (see below).

Regarding the methods, hopefully a more senior Blender user will correct me if I’m wrong here. (I’ve only been using it since August).

The first method you descibed appears to be using an Empty to keep an objects texture in tact when radiosity is being calculated, which normally dosen’t happen (more on radiosity and textures)

The second method is used to have an Empty act as the point of view to calculate an Env Map from. Refl sets up the texture coordinates to appear on the object as a reflection. Note: I rarely use an Empty for Env Maps (non radiosity renders).

I usually enter the object’s name in the OB: field, then set it up to render all the layers except the layer that my object is on. Objects use thier pivot point (little purple sphere) as a ‘camera’ to calculate an env map.

For example set up your object named ‘sphere’ on layer 3 with an env map using OB:sphere, making sure you set the option so it does not render layer 3. It will calculate the env map minus the sphere. Refl will make sure it maps ‘correctly’ (in most cases).


(marcanth) #7

:slight_smile: I guess I understood your explanation. So, you mean that for non-planar (sorry my english) reflections, there is no difference if I use an empty or not? Indeed, I saw strange results while trying to make some tests with envmap (without empties). Well, I have to explain that the strange result happens to me when I put a Shpere, lights, plane and everything else in the same layer and add a “World” environment, you know, where you can change background color, create some stars, etc. So, considering the default settings (gradient with blue and black), and that I put the camera a little above the default position and when I render it I get a strange reflection. Have you seen that? Well, I hope you understood what I am trying to tell? Sorry if my English is not so good…

Thanks for helping! Each day I am learning a little more about Blender and enjoying it a lot :slight_smile:


(ec2) #8

I could explain it (I think). But run through this tutorial It discusses Env Maps in greater detail.

Then you will read better explantions of how env maps work. You learn more by trial and error.

If other members reading this have links to offer please do.

Also try searching for env map in the search engine on this site for more info.

Lastly, in the Tutorials section on this site there is a reflection tutorial.

Keep going. It take practice. No problem with helping. We all need it.


(marcanth) #9

Thanks, ec2.

Actually, I already read that tutorial (not entirely, have to practice the last one, with many reflecting spheres). I have seen many tutorials about reflections, but they say different things, and those settings I put here I saw from these tutorials… I did an experience today, but right now I am a little confused about the method (with the empty). I will post it here soon… LOL


(ec2) #10

Here is another great tutorial.

BdgM’s Spherical Env Map Tutorial

Good luck!


(marcanth) #11

:slight_smile: Thanks, ec2. I will check this tutorial too… Well, I must confess that I already had donwloaded this tutorial. Pretty interesting and valid… However, the “reflection” is the same of the mountains behind the ball. Well, anyway, this is valid, because we can learn how to make reflections and things related. For a true reflection, in this case, what the ball would reflect, we would not be able to see, right? That would be behind the camera. Well, I must say that, however, we get good results doing reflections this way too, so it is valid. I was used to make this kind of reflections using the very interesting 3D Studio 4.0, for DOS, I guess you remember? With 3DS 4 it was pretty easy to set a lamp to make radiosity, if I remember well and we even had “projector lights”. Well, I guess that this is what we have now in Blender Publisher 2.25, isn’t it?

Sorry not to return yesterday. Got some things to do. Anyway, I have read here that many people like to use envmaps to make reflections, which is valid in many cases, but I think that it has some problems as the reflections aren’t as good as those when we use an empty. Well, this is what I think, according to some experiences… Even using just the envmap (with no empties) and putting the sphere to another layer and adjust the envmap not to render that layer, the result is still problematic, or maybe I could be doing something wrong, but I will be able to find out more exactly just when I follow these tutorials you mentioned.

I was thinking about something… Would Blender invert a reflection (upside down) if we use a “concave” mirror? Just like when you see yourself in a polished (new one) spoon? I will check this… just curious…

I may seem sometimes a little perfectionist, but I am just curious to learn what can be done and what cannot… and how to achieve a good result. Well, I have a lot to learn… and love to.

Thanks ec2,
Andre