Sometimes you may come across the simple need of fading an object in or out. The first idea a new user usually gets is to use the Transparency Channel of a Material. That’s a bad choice because you’ll very likely use the material on several objects and they will all be affected then. Or your object has more than one material and so every material channel has to be manipulated. Until we don’t have support for a node based material system in Cinema 4D this isn’t the way to go. And honestly fading an object in or out shouldn’t be done by changing material attributes.

Better use the visibility option in the Display Tag. This is a much better idea but you’ll run into some unpleasant things as well.

When this object consists of overlapping geometry, it might look like this:

This might not be the eye-candy quality you are looking for. In addition to looking plain ugly in most situations rendering with using the visibility option for transparency will increase render time by the factor of 2 and more. Not only it strains your eyes, it also strains your time.

A common reply for solving the fading-issue in the forums is “do it in post”. And that is a perfectly valid way to approach this task if you have a compositing software by your site. But what if you don’t own a copy of After Effects or another costly Compositing Software?  Don’t give up. With a little tweaks we make this damn display-tag to work in our favor.

1.Grab yourself a compositing-tag and throw it right on fading object. Right beside the display-tag.

2. Bring the “Exclusion” Tab of the Compositing Tag to the front and drag your fading object into the exclude-area.

3. The little icons behind the objects name look per default like this now:

What do they mean? Unfortunately you wont get any hints by hovering your mouse-arrow over these symbols. From left to right their name is:

• Transparency
• Refraction
• Reflection
• Hierarchy

The first 3 items in this list name render-attributes of an object. You can activate or deactivate these render attributes here. This gives you the option to i.e. deactivate the reflection of another object.

The hierarchy item in the list defines whether only the object in the list should be considered here or all his child-objects as well.

You can read the default setting as: Deactivate the refraction and reflection of the listed object and all its children for the object which carries this tag. But what we want is different. We want that our transparent object isn’t affected by it’s own transparency. Sounds weird? I agree. It’s complicated to explain only with words. When you look at the third image in this post you’ll find that the vehicle itself shines through its own transparent geometry.  To avoid that apply these settings:

Be sure that the object that carries the tag is the same object as the one in the list. It reads now: Deactivate the transparency of the listed object for the object which carries the composite tag. Need a hint to learn these settings? Just click every of the first 3 icons once. Because this is the exact opposite of the default state.  Enough with all the talking. Let the result speak. Hit Render! This is the resulting render:

Now you can start fading objects in and out directly in Cinema 4D. Of course this works with stills as well as with animation. Isn’t that great?

If you have any ideas to improve this tutorial, or problems to get the right results make use of the comment feature.

Recently I came across the following problem in C4D: an object in a building had to cast shadows everywhere except for one wall. The “special” wall would receive shadows from other objects, but shouldn’t show any trace of a shadow of my particular object.

This sounds more simple as it is to do in C4D. Read on for my solution.

The problem

In the example scene are a cube and a cylinder in a corner of a room. One spot light illuminates the corner, casting shadows of the objects onto the walls. For some reason I want to get rid of the shadow cast by the cube onto the right wall. Marked red in the image below. A simple task maybe. Put in a simple sentence: the green cube must not cast a shadow on the right wall.

If you want to control lights and shadows you usually go to two destinations first in C4D. The scene tab in the settings of a light source or the settings of the compositing tag.

The Scene Tab

Lets look  at the first. In the scene tab I can exclude objects from the influence of the light. It has two modes. Exclude and Include. If you use Exclude, which is default then all objects in the scene are influenced by the light except for the objects in this field. If the light is in Include mode no object at all is influenced, except for the objects in this field. When you drag and drop an object here it looks like this.

The 5 icons behind the object are specific attributes of a light source which can be de- or activated here. From left to right:

1. object (just for recognition, doesn’t do anything)
2. illumination
3. specularity
4. shadows
5. hierarchy (if the children objects are affected by the settings here)

In the above picture every icon is active and therefore every aspect of the light source will be excluded for the chosen object AND all its children in the hierarchy. Since I want to get rid of the shadow of the cube I have to activate only the shadow icon.

The resulting image:

Great. I got rid of the cubes’ shadow. And only the cubes shadow! But wait! Every shadow of the cube is gone and not only the shadow on the right wall. That’s not what I am aiming for here, since I want to get rid of the shadow of the cube on the right wall only.

Here’s the limit of the scene tab settings. It allows only for global shadow manipulation.

The next way to handle the problem might be

The Compositing Tag

The shadow related settings in the Compositing tag are

• Cast Shadows
• Receive Shadows
• Self Shadowing

These are again global settings. If I give the right wall a Compositing Tag and turn “Receive Shadows” off, the wall wont receive shadows from the cube. But no shadows from the cylinder and any other object in the scene as well.

This rendering shows how it looks when the wall doesn’t receive shadows:

It seems that there is no simple button in Cinema 4D to cut the light/shadow-cast connection between 2 objects. Or put it again into a simple sentence: Its not possible to tell the green cube to not cast a shadow on the right wall. And leave everything else as it is.

So but what is the way to accomplish this seemingly easy task?

The solution

I had a discussion on this in a German c4d forum. One user suggested doing it in Postproduction. Rendering an Alpha channel for the right wall would provide a cut out template for the shadow of the cube which would be rendered separately as well. This is a way that should work. But there is a way to do it in Cinema 4D as well.

For this we have to work with two copies of the same light source.  The first light source works in Exclude Mode. The green cube and the right  will be dragged into the objects field. Deactivate the shadow icon. This light doesn’t illuminate the scene. It only cast shadows. This is how the rendering looks:

It looks like there are no shadows on the right wall. But that’s not true. In fact the wall is full of shadow. Its the absence of light which makes the shadows invisible. So we need a second light for this. A light with the exact values of light 1. A copy.

The second light works in Include Mode. The green cube and the right wall are dragged into the objects field again. Only deactivate the Shadow Icon again. Because the light is in Include Mode now the settings have the opposite effect. This light only illuminates the objects and doesn’t cast any shadow. Here’s how it looks:

And now both lights combined:

It looks a bit like the image above where the Composite tag of the right wall prevents the wall from receiving any shadow. But look closer and you’ll see that the wall receives shadows from diffuse light sources in the scene. Only no shadows from our 2 central objects.

We’re almost there. The one thing which is missing is the shadow of the cylinder on the right wall. Drag the cylinder into the second light’s scene tab and deactivate any icon except for the shadow. This way only the shadow of the cylinder is added to the scene without any extra illumination on the cylinder. Voila, the result:

And here are the settings in the 2 identical lights:

Nice trick, isn’t it?

(Apologies for any grammatical errors, I am not a native English speaker

In the last days I had the time to dig into the topic “animation export”. Here is what I found out. First I have to say that I work on a Windows Computer and many of the following tips are only valid for the windows platform, because of the absence of some plugins on the Apple platform. Sorry. Not my fault. I work with Cinema R11, but the plugins I use in the following short tutorial are a bit older, so they should work with older versions of C4D, too.

During the last weeks I found 3 ways to bring  animation data from  Cinema 4D into Blender. I mention the first 2 ones here, because they exist “theoretically”. I didnt have much success with these ways.

1. md2 export with the plugin “animesh”
2. collada export
3. mdd export with the plugin “mdd writer”

Animesh:

This plugin exports an ams file which in a 2nd step has to be converted to a md2 file with the executable amstmd2.exe which comes with the animesh plugin in the plugin directory of the cinema folder. (md2  is an old format of the quake engine) This works hassle free. I wish I could say the same thing about the md2 importer of Blender. Sometimes it works but most of the times it’ s not. Instead it stutters some script errors, which are mysteries to the inadept. It worked for me one day, so I want to mention it here. But for some unknown reason to me, I must have raised the wrath of the gods and Blender will not import the md2 files anymore. Maybe it works for you. When it worked on my computer I was able to export Position/Scale/Rotation Animation. I couldn’t test PLA Animation.

Here is the link to the animesh Plugin.

Collada:

Collada is a  format for Cinema 4D since the release of version 11. It is an open xml based format which was invented as an 3D exchange format by the gaming industry and is supported by many 3D software packages, one of which is Blender.  As far as I found out Collada only supports Position/Scale/Rotation animation. No Vertex animation. Although it should support Mesh Morphs. But I dont know how to export this data from Cinema 4D. At least I couldnt achieve more. Cinema 4D writes a collada file with the version 1.4. So the proper Blender Importer (1.4) should be used. But before importing anything into Blender a bit manual work is necessary, because Blender chokes on the dae file from C4D resulting in no animation at all in Blender.

Open the collada file in a text editor. Search for the tag <library animation> . Cinema nests all animation data tags in one surrounding animation tag. This seems to be unreadable for Blender. So just remove the surrounding tag. Instead of:

<animation>
<animation></animation>
<animation></animation>
<animation></animation>
</animation>

It should look like that:

<animation></animation>
<animation></animation>
<animation></animation>

I wont go into more details about using the collada format, because I had hard times with the collada importer of Blender besides the problems with the file structure. The importer simply refuses to work sometimes, which makes it a pain to work with.

This leads me to the last option which I would recommend because it worked more reliable than the other options for me.

MDD Writer:

The .mdd format saves animation as vertex animation data in an additional  mdd file. It only saves vertex animation. No Position/Scale/Rotation. Here are the steps:

1. select the .mdd writer plugin from the plugins menu. This will create a .mdd writer object in the object manager.

2.use it to export every object which takes part in the fluid simulation and save the according  .mdd file(s).the .mdd file only holds the animation data. Not the object itself.

3. export the objects which you have exported as .mdd files in the previous step as single .obj files. Scale factor for .obj export should be set to 100.

4. now import your obj file(s) into blender and make sure that the option “morph target” is set. Otherwise Blender will mess with the order of the vertices of the imported objects and this will lead to funny results in the animation.

5.Select one of the  inported objects within Blender and then import the .mdd file with File->Import->Load MDD… This should write the animation data into the selected object. Repeat this for every object which has an according .mdd file.

Now you can setup your fluid simulation in Blender.  All imported animated objects are set to obstacles, the Boundary type must be “NoSlip”  and the option “Animated Mesh:Export” must be activated.

Here’s the link to the mdd writer plugin.

And here’s a simple example of a Bouncing Ball in a pool of water:

Bouncing Ball in Blender Fluids from bernd salewski on Vimeo.

In my post from last year I have described in a summarized way how to use the fluid simulation of Blender with Cinema 4D. My conclusion at that time was that it is doable but you run into limits every way you turn, mainly because of the huge memory consumption caused by loading all frames of the animation into a c4d scene at once.

In the last weeks I had some time to play with Blender Fluids again.

This time my main interest was if the new xRef objects can be used to reduce the memory load by only referencing one fluidmesh per frame. A guy in a german Cinema 4D forum told me that of course it’s possible: Just reference the old, big, fat c4d-file (the one with the visibility flip switch, see my previous article) in a new file with an xRef object. Hit the button “Take Animation” and the fluid container file will play through the xRef. That sounded promising and I tried that way. But it still needs a lot of ram because when the xRef takes the animation from the referenced object, it doesnt only take the current frame. It loads much more. I can’t say what exactly. The memory load is smaller than as having the container file itself opened, but its still very high and you can imagine that with a more complex setup you will run into walls a bit later. But they are still solid.

So I experimented a while with my limited coffee skills and finaly my wasted hours where rewarded. I created an enhanced xRef object which will reference the fluid simulation and only loads one mesh at a time into memory. I feel very happy about this, because it allows for much bigger fluid simulations in Cinema 4D.

Here’s an overview of how it currently works. This is not a Blender Tutorial.

1. Export your scene into .obj format.

Scaling factor = 1; Only the objects which are part of the fluid simulation.

This is for non-animated objects. Windows users can try the animesh-plugin for exporting animated objects via the .md2 format. m2d allows for position/scale/rotate animation as well as PLA Animation. Or try Collada, which is available in the new C4D 11 Release. Collada doesnt allow PLA as far as I know.

2. Import your scene into Blender with the wavefront importer.

This should work pretty much without running into problems.

3. Set up and run the Fluid Simulation

There is a comprehensive  reference on all the settings on the blender site.

4. Export the Fluid Mesh as an animated Mesh via wavefront obj.

You will get one .obj file for every frame of the simulation. Deactivate “Material” in the export options, because you don’t want to export Materials. Activate “Animation” and “Selected”. Make sure that the Domain Object of the Simulation is selected while exporting.

5. Run a batch search/replace tool on the sequence of obj files.

You can use the freeware Replace in Files for that. Replace the line “usemtl(null)” with an empty string. This is done because it avoids having a default material sitting on every fluidmesh in the obj files. Which is a problem if you wanna define your own water material later on.

Update 8.12.2008: There is another way to get rid of the default materials in the obj files which is less hassle. Open the file “export_obj.py” from the Blender script directory in a text-editor. Search for the 2 lines starting with:
file.write(‘usemtl
Put a # in front of the lines to comment them, so that they dont get executed.

This should get rid of the hassle to batch replace the materials in the obj files.

6. Use my provided enhanced xRef to reference the fluidmeshes in your scene.

Download the xref object here.

The xref has 3 user settings.

1. filename:

reference the first file of the sequence here.

2. counter length :

this refers to the number of digits in the filenames. like”filename_0001.obj”. Adjust the numbers of digits in the filecounter here. In this example it would be 4.

3. animation offset:

adjust with which frame the animation should start. negative values allowed. A value of 25 would start at frame zero in the cinema timeline with the 25th fluidmesh in the sequence.  A value of -25  would start with the first fluidmesh at frame 25 of the cinema timeline.

Probably you have to scale up the xref by 100 to get size of the fluids fit into your scene.

7. render your animation

and feel happy about the very low memory load of the fluidmesh.

This short article is NOT a comprehensive tutorial about using Blender together with Cinema 4D. It’s targeted at people who know how to setup Blender fluids. And who just wanna know how to use the fluids together with Cinema 4D in a memory friendly way.

I have already produced a video tutorial in german language where I speak about all this in a more detailed way. I am planning to release one in english, too. When I find the time to do so.

I hope this article will help some people to manage Blender Fluids and come up with some decent renderings of fluids in Cinema 4d.

Update: I added this short test animation where the above image was taken from.

Blender Fluids Example from bernd salewski on Vimeo.

So I started to play around with the fluids in Blender.

Fluids are cool. They are fun. Cinema 4D has absolutely no fluids yet, so I was interested in combining Blenders Fluids with Cinema 4D. The connection is possible but not satisfying yet.

1. Model your scene in C4D
2. Export it via Wavefront obj. format
3. Import the scene in Blender
4. Set up the Fluids in Blender (define the fluid, the simulation space, the obstacles, …)
5. Render the simulation (and take a walk in the meantime )
6. Export the Fluids as an animated mesh in .obj format, this will give you one file for every frame
7. Import all the files in C4d via the contentbrowser
8. Use this script which sets all fluid meshes invisible, excluding the mesh fo r the particular frame

The big drawback is the memory-usage. You’ll need a lot of ram to render a halfway decent simulation. This is because all fluid meshes are loaded into the memory at once, even the meshes which are not used at a particular frame. A plugin or skript which loads only the mesh which is needed at the current frame would do the trick here and allow for more complex scenes. But I couldnt find one so far.

Watch my fluids animation here (Fluids: Blender, Rendering: Cinema 4D):