Development Journal of a Raytracer

Topological Representation Object - 5

nospam@example.com (Josef Meixner) — Fri, 19 Mar 2010 22:23:39 +0100

Not quite done yet, but now setting the path to an object should work. I have one small issue where I might have to change something, but have not yet an idea of how to do it. It would only be noticeable if for an object a path was set and then at the same object, through a different path a new path would be set as referenced object and that was undone. Then the transformation matrix would be wrong (the reference to "self" would be to the second path of the object and not the first).

The problem is, that it could be happening and I am sure it would lead to a lot of confusion, so I might actually try to fix that problem. If I find a good way. But apart from that problem I should have all the major issues covered. The rest should be easy and then I hope to finally create the images for the new objects. After that I will probably add the last big thing, selecting the object visually. I even have an additional idea, in the case of the socket I could not use the selection, as the object in question is invisible (it is a box only used to cut out a hole from the wall). So it might make sense to allow selection of a group and then only present the objects in that group. Though I have not yet an idea of how to do that in my UI.

Track Texture - 8

nospam@example.com (Josef Meixner) — Thu, 18 Mar 2010 21:37:20 +0100

This week I managed to implement the checks for the track slices. And I started on the algorithm to find the points, where the slice changes. I haven't come far with that, but the check-function at least gave me some ideas of how to continue. The biggest problem is the flexibility I have built into the format. I think I should be able to write the function next week, at least I hope so. I slowly would like to get on with this thing.

Channel Material - 34

nospam@example.com (Josef Meixner) — Wed, 17 Mar 2010 21:54:42 +0100

I removed some of yesterdays code and did it in a slightly different way. The reason is, that I had a, I think, good idea. Yesterday I stored the assignment of storage to the pins directly in the pins, but that means, I can have only one mapping (or it gets very ugly). But when thinking about how to continue I found out, that I will soon want to have the ability to see, what an arbitrary channel will create. And for that I need to be able to evaluate the operators. For example I would like to have an operator which mixes two images using a third one, so that the first image is superimposed with the second whenever the control images intensity is over for example 0.9.

But that will be much easier if I can actually see the images. So I would want the UI of the operator doing the mixing to be able to display the three input images and the output image. That way I can visually change some settings. In general I will probably not put the images into the operator UI, but into some other place so that changing operators doesn't close them. E.g. if the control image is done by some procedural noise function I would probably like to see, what happens to the output if I change the settings of the noise.

Topological Representation Object - 4

nospam@example.com (Josef Meixner) — Wed, 17 Mar 2010 21:46:07 +0100

As I wrote yesterday, I started with the gathering of the list of objects. The objects have to match some criterion (it is done with a simple function which receives the object and then returns true if the object can be used) and now there is a function which gathers all objects in the scene and records their path. Up to now I only had a function which returned the object which were directly contained by some object, so it could not look into groups.

The code is untested, but on Friday I hope to start using it. As soon as it is working I will try to get the rest of the new class into a working state, the visual selection thing is secondary. I rarely used that in the past, so I guess not much harm is done to postpone it. But getting the old code removed and the new one taking over is an important step.

Channel Material - 33

nospam@example.com (Josef Meixner) — Tue, 16 Mar 2010 21:55:19 +0100

I have also made some progress on the Channel Material. The preprocessing function is working now and each used pin should now know where to find data or where to put it. So next is actually evaluating the operators to create a texture of the Channel Material I can use in OpenGL. I can't really represent the shader models (e.g. Ward BRDF) and only get a very coarse idea what the material will look like, but I guess that is ok for now.

What would actually be possible is, to create a real OpenGL shader program to load directly into the GPU. But that will be something to be done at a different time, I guess.

Topological Representation Object - 3

nospam@example.com (Josef Meixner) — Tue, 16 Mar 2010 21:43:36 +0100

The function to find the complete path of the first object is working. I haven't tested it thoroughly, I only put a box in a group, but that worked well and is all I need for now. Now the second part, selecting another object. I have been thinking about some ways. The current code lists all objects of the right type which are directly contained in the model. It would be great, if I could also add the objects in the groups and identify them. I am not sure if I should do so, it would be possible, but still the list might get prohibitively long in complex scenes.

But perhaps it is best to implement it and worry later about that problem. There are always ways to structure the list, once I see, how I really use the program when I have huge models consisting of many objects. So I guess I will add them and as name use a concatenation of all names of the path leading to the object.

I have also had an idea how to select the object visually. Currently I can only select an object, then look into it and in case of a group select one of the contained objects. But that is only a limitation in the API, the hit stack created by OpenGL should actually make it possible to directly get the path. I guess I will have to implement that operation, it is way too useful and I guess I will use it in some parts of the program. If not now, then in the future.

Topological Representation Object - 2

nospam@example.com (Josef Meixner) — Mon, 15 Mar 2010 21:39:55 +0100

I continued with the object which will store the necessary data to calculate the transformation matrix from one objects coordinates into another ones. The code to load and store the data is completed for now, I will have to extend it, as I have to connect callbacks to the loaded object, something I haven't done yet. I have also started to implement the function to create the UI (it isn't doing much at the moment) and I have added the object to the CSG-modifier.

Then I started to implement a function to find out the first half of the mapping, the sequence of ObjectPointers to the object which includes the object. I think, I can get that information from the selection, as my selection objects always contain a pointer to the parent selection. The parent selection is the selection which was active before and that contains pointers to the object which was selected before the current object was. So I hope I can reconstruct the path through the object hierarchy with that information.

That is the easy part, then I have to implement the selection of the second object. I am still considering different options for an UI. And I will probably add an editor to select the object by clicking it. But there too I am not sure yet, how to implement it. But at least the first steps are clear, I will add all the necessary code to add the features I currently have so I can start to remove the old code and switch over as soon as possible.

Compression of HTTP Responses - 2

nospam@example.com (Josef Meixner) — Sun, 14 Mar 2010 21:54:53 +0100

I also worked on the HTTPD. Compression is still not implemented, but today I added the code to create the necessary "content-encoding" header and also wrote the support code to send the compressed data. All that is missing now is the function which compresses the data.

I looked into the zlib documentation, but I will need a bit of time to get that correctly implemented. One of the bigger issues is the amount of memory needed for compression. By default the zlib allocates about 256K Bytes per compression channel. I think that is too high for what I try to do, most web pages are by far smaller than that and so I hope that the compression actually doesn't suffer when I reduce the amount allocated. I think, that using 1GB per 4000 HTTP responses is quite high and I want to be able to have such an amount in flight. As my server is going to be single threaded it can actually happen, that connections waiting for operations e.g. on a database to complete can already have a compression channel and so it might be possible to queue up a lot of channels and so take away a lot of memory.

Channel Material - 32

nospam@example.com (Josef Meixner) — Sun, 14 Mar 2010 21:49:57 +0100

I also worked briefly on the Channel Material. The first part of the preprocessing is done, I have a list of operators to evaluate and the list of default values I will need. Very important in this is, that the list of operators is ordered so that the evaluation of an operator depends only on the default values and the values calculated by operators before it. So now I will run through that list and "allocate" memory for the operators and tell the operators where they find their input values. The memory is not really allocated, that will be done when evaluating the structure, I only need to calculate the size of memory needed and give the memory map to the operators.

Topological Representation Object - 1

nospam@example.com (Josef Meixner) — Sun, 14 Mar 2010 21:38:59 +0100

I guess the title is scary, but it is actually quite easy what I started today. To finally get the socket into the wall, I need the ability to cut out a hole. As I still haven't fixed the problem in the CSG, that it needs at least one edge of an object to run through a closed loop of the other, I implemented the huge change to the edge loop modifier, which I finished yesterday.

So what is keeping me from adding the socket is, that the box I need for cutting the hole is part of the group which combines the elements of the socket. And I can't access that object from the CSG-difference. The problem is, that the current code can only access two object pointers, one I need for the wall, the other would be the box. But as it is in a group, I wouldn't get the full transformation. The problem stems from the ability of my program to recreate the geometry, therefore I need access to the object after I have defined the CSG-operation. Worse, I want it to react to any changes in position and so it has to have the ability to get the complete transformation. For the user that means I want to be able to move the socket and the hole is supposed to move together with it.

To finally fix this problem, I started with a new object which will store pointers to all the relevant objects so I can recalculate the transformation. As that is basically the topological information it should explain the strange title. Currently not much is working, the object exists and it has some storage for information. But only storing is implemented, I still have to add loading tomorrow. It is quite hard to tell, how long I will need for this thing, but I hope it will be easier than the last thing.

Edge Loop - Numerical Control - 8 - Finished

nospam@example.com (Josef Meixner) — Sat, 13 Mar 2010 22:34:55 +0100

Today I implemented the rest of the code to finish the still open problems. The edge loop now has a nice little label to show the direction of the edge being split. That way numerical control is possible and I already played a little bit with it and it works quite well. The biggest problem was to add some form of minimum size for the label. The code I had written was completely ok, but it didn't work.

At the time I thought I had done something wrong and tried some other things, but in the end I found out, that the multiplication of a vector with a matrix was wrong. It didn't use the values of the fourth row. Normally not a problem as the usual affine transformations have a last row consisting of 0, 0, 0, 1 and that can be ignored. But as I had to transform a vector by the projection transformation it resulted in wrong results, as that matrix has a very different last row (it is not an affine transformation). So in the end I found a very, very old bug and made the program a bit slower, but at least now it works.

Edge Loop - Numerical Control - 7

nospam@example.com (Josef Meixner) — Fri, 12 Mar 2010 23:11:00 +0100

I have continued a bit on the edge loops. It is always quite some work to get something into the OpenGL-renderer, as I have to be careful to not bind the modeler core to OpenGL. I hope to finish this thing tomorrow and then continue with the room to finally create some renderings for the socket and the light switch.

It might sound excessive to go to such lengths to get some renderings for two small objects, but I had problems to do those renderings quite often in the past. So I want to finally fix these problems so that I can create the necessary models more easily in the future. The features will be useful in future models, I am very sure of that.

Track Texture - 7

nospam@example.com (Josef Meixner) — Thu, 11 Mar 2010 22:05:49 +0100

Last week I didn't do anything, but at least this week I have started on the code to create the geometry to handle the track textures. The first function I need is to define where I have to put the slices. When I started to add it, I noticed there was something missing, I had not added some form of sanity checks, so even completely useless definitions could make it into the algorithm.

To make it at least a bit easier I decided to first check the slices. There are a number of conditions which have to be met. E.g. there has to be at least one slice, at least one slice has to be flexible in width and if there are fixed alignment positions they have to be in a rising sequence. Also the first slice has to either be anchored to the position 0 or at least be able to fill the track all the way to the left edge. The same is true for the last slice, it has to be able to fill the track to the right edge.

I hope, I can implement all the checks next week and perhaps even start on the distribution algorithm.

Channel Material - 31

nospam@example.com (Josef Meixner) — Wed, 10 Mar 2010 21:48:42 +0100

I am back at where I was before I started to implement the shader operator. I guess for now I will try to implement what I have currently and then see, how to fix the rest of the problems. So as the default model of the Channel Material is now nearly a working version (I didn't define the shader to use, I basically have an empty container), I hope to finished the preprocessing step and then implement a simple OpenGL-version of the material. It will just create a texture and then use a Phong shader.

Edge Loop - Numerical Control - 6 and Channel Material - 30

nospam@example.com (Josef Meixner) — Tue, 09 Mar 2010 21:37:22 +0100

Edge Loop

I added a new UI-control to show the length of the edge being split. So now only the second part is missing, adding a transparent quad with a texture with a "+" and a "-" on it to show in which direction the edge will move.

Channel Material

I have defined all the necessary pins for the shader model. When doing so I also thought about the next steps and there are some problems. One is, that the raytracer uses quite different data and for example handles antialiasing whereas the OpenGL-renderer doesn't. I will have to think about a way to handle that, I only have an idea at the moment. If possible I would like to avoid to implement the operators twice, once for OpenGL and once for the raytracer.