I am developing an isometric game in Java2D. I.e, note that I do not have direct access to hardware pixel shaders (real-time software pixel shaders aren't practical. I can do a single pass on every entity texture without a noticeable hit on performance)
I know the typical method would be to somehow encode the depth of the individual pixels into a depth buffer and look that up. However, I don't know how I can do that efficiently in Java2D. How would I store the depth buffer? How would I filter out the alpha in an image? Etc.
Up until now I have just been reversing the projection matrix I use to calculate the tile-coordinates. However, that doesn't work well when you have entities that render outside of those tile's bounds.
Another method I considered was using a color-map, however I have the same problems with this as I do with the depth buffer (and if I can get the depth buffer working I'd much rather use that.)
Here is a picture of what I am working with:
I've resolved this quite nicely. The solution is actually very simple, just unconventional.
The graphics are depth sorted via a TreeMap, and then rendered to the screen. One can simply traverse this TreeMap in reverse (and keep it until the next render cycle) to translate the cursor location to the proper image it falls over (by testing the pixels [in reverse render order] and checking if they are transparent.)
The solution is in the open-source project, under the io.github.jevaengine.world.World class, pick method. https://github.com/JeremyWildsmith/JevaEngine/blob/master/jevaengine/src/main/java/io/github/jevaengine/world/World.java
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I am currently designing and developing a bespoke imagery viewer for exceptionally large image files (sometimes in the gigapixels). Fortunately these are provided as 256x256 tiles in staged resolution layers, then passed across to OpenGL when required.
The tiles themselves are managed via a QuadTree which seems like a strong solution for "almost power-of-two" images. However given an image with a extremely wide aspect ratio (e.g. 1 gigapixel x 50,000) the model starts to falter with large amounts of null tiles.
There will only ever be a limited number of tile's on display at a time.
I am using Java 7 with LWJGL to provide an OpenGL Context.
Does a QuadTree solution fit this problem, or are there better alternatives to managing the data?
Edit: Edited the title to make more sense.
The quad tree enforces that you split along both coordinate axes. Your problems has a wide aspect so one of the axes will be oversplit.
You have 2 solutions:
Use BSP. Similar concept but instead of spliting both coordinate ranges you pick one and split that into 2. With this you can split along the large range more often than over the smaller one.
Use grid of QuadTrees at the top level. This way you split the space into rough squares so that you make better use of the bits. This was also suggested by #Andreas in the comments.
I am writing a game on Android, and it is coming along well enough. I am trying to keep everything as efficient as possible, so I am storing as much as I can in Vertex Buffer Objects to avoid unnecessary CPU overhead. However the simple act of drawing lots of unrelated primitives, or even a varying length string of sprites efficiently (such as drawing text to the screen) is escaping me.
The purpose of these primitives is menus and buttons, as well as text.
For drawing the menus, I could just make a vertex array for each element (menu background, buttons, etc), but since they are all just quads, this feels very inefficient. I could also create a sort of drawQuad() function that lets me just transparently load a single saved vertex array with data for xy/height&width/color/texture/whatever. However, reloading each element of the array with the new coordinates and other data each time, to copy it to the Float Buffer (For C++ guys, this is a special step you have to do in Java to pass the data to GL) so I can resend it to the GPU also feels lacking in efficiency, though I don't know how else I could do it. (One boost in efficiency I could see is setting the quad coordinates to be a unit square and then using Uniforms to scale it, but this seems unscalable).
For text it is even worse since I don't know how long the text will be and don't want to have to create larger buffers for larger text (causing the GC to randomly fire later). The alternate is to draw each letter with a independent draw command, but this also seems very inefficient for even a hundred letters on the screen (Since I read that you should try to have as few draw commands as possible).
It is also possible that I am looking way too deep into the necessary optimization of openGL, but I don't want to back myself into a corner with some terrible design early on.
You should try looking into the idea of interleaving data for your glDrawArrays calls.
Granted this link is for iphone, but there is a nice graphic at the bottom of the page that details this concept. http://iphonedevelopment.blogspot.com/2009/06/opengl-es-from-ground-up-part-8.html
I'm going to assume for drawing your characters that you are specifying some vertex coords and some texture coords into some sort of font bitmap to pick the correct character.
So you could envision your FloatBuffer as looking like
[vertex 1][texcoord 1][vertex 2][texcoord 2][vertex 3][texcoord 3]
[vertex 2][texcoord 2][vertex 3][texcoord 3][vertex 4][texcoord 4]
The above would represent a single character in your sentence if you're using GL_TRIANGLES, and you could expand on this idea to have vertices 5 - 8 to represent the second character and so on and so forth. Now you could draw all of your text on screen with a single glDrawArrays call. Now you might be worried about having redundant data in your FloatBuffer, but the savings will be huge. For example, in rendering a teapot with 1200 vertices and having this redundant data in my buffer, I was able to get a very visible speed increase over calling glDrawArrays for each individual triangle maybe something like 10 times better.
I have a small demo on sourceforge where I use data interleaving to render the teapot I mentioned earlier.
Its the ShaderProgramTutorial.rar. https://sourceforge.net/projects/androidopengles/files/ShaderProgram/
Look in teapot.java in the onDrawFrame function to see it.
On a side note you might find some of the other things on that sourceforge page helpful in your future Android OpenGL ES 2.0 fun!
I'm using JOGL (OpenGL for Java) for my application and I need to draw tons of strings on screen at once and my current solution is far too slow. Right now I'm drawing the strings using TextRenderer using the draw3D method and for even a moderate number of strings (around 300-500), it just kills the FPS. I started messing with drawing text onto the object textures, which is much faster, but there are a few problems with it. The first is that allocating all those textures requires a lot of memory. The second is that I need to find a way to size the texture so its only as big as the string and then map it to the object without stretching. The problem there is that all these thousands of boxes are using a single model being rendered with a call list. I'm not sure its possible to change the texture mapping for each object in that situation.
I don't mind if the text appears flat or 3D, it just has to be positioned in 3D space. I would prefer to render the text in the highest quality possible without sacrificing too much speed, since readability of the text is the most important part of the application. Also, nearly all of the strings are different, there aren't many duplicates.
So, my question: Am I going down the right path with drawing the strings on the textures, and if so, how can I overcome those 2 problems? Or is there another method that would suit my needs?
Depending on exactly how TextRenderer works - you might be able to use display lists to batch up your text drawing commands.
If TextRenderer works by having a texture of individual character glyphs and piecing together a string a glyph at a time: it'll be fine. just bookend your text drawing code with glNewList and glEndList. Once a list is defined, just use glCallList to use it.
If however, TextRenderer works by drawing complete strings into a texture and using one quad per string - display lists may not work. If the strings in one batch do not all fit within TextRenderer's cache, it will delete the least-recently used one to reclaim some space. Display lists will only recreate the OpenGL calls made, and so the work done by TextRenderer to update the string cache texture will be lost and you'll get incorrect output. From a quick scan of the source, I suspect that TextRenderer works in this manner.
To summarise: Display lists will greatly speed up your rendering, but will only if you don't overflow TextRenderer's string cache texture and don't use the TextRenderer after the display list has been defined.
If you can't meet these constraints you're going to have to go a bit hardcore and write your own text renderer that renders glyph-by-glyph - it'll then be trivial to cache the output geometry and extremely quick to re-render. There's an example of such a system here, with the tool to create a font here. It uses LWJGL rather than JOGL, but the translation between the two will be the least of your worries if you want to integrate it - it's meshed with the texture management etc.
I'm trying to develop side scrolling game for android involving many many textures so I was thinking if I could create a separate layer, all a single unique color (very similar to a green screen effect) make a collidable and make it invisible to the player.
(foreground layer) visual Image
(2nd layer)collidable copy of foreground layer with main character
(3rd layer)Background image
I not sure if this is possible or how to implement it efficiently, the idea just came to me randomly one day.
Future regards, Thanks
I assume your game is entirely 2D, using either bit-blits or quads (two 3D triangles always screen-aligned) as sprites. Over the years there have been lots of schemes for doing collision detection using the actual image data, whether from the background or the sprite definition itself. If you have direct access to video RAM, reading one pixel position can quickly tell if you've collided or not, giving pixel-wise accuracy not possible with something like bounding boxes. However, there are issues greatly complicating this: figuring out what you've collided with, or if your speed lands you many pixels into a graphical object, or if it is thin and you pass through it, or how to determine an angle of deflection, etc.
Using 3D graphics hardware and quads, you could potentially change render states, rendering in monochrome to an off-screen texture, yielding the 2nd collidable layer you described. Yet that texture is then resident in graphics memory, which isn't freely/easily accessible like your system memory is. And getting that data back/forth over the bus is slow. It's also costly, requiring an entire additional render pass (worst case, halving your frame rate) plus you have all that extra graphics RAM used up... all just to do something like collision-detect. Much better schemes exist, especially using data structures.
It's better to use bounding boxes, or even a hierarchy of sub-bounding boxes. After that, you can determine if you've landed on the other side of, say, a sloped line, requiring only division/addition operations. Your game already manages all the sprites you're moving, so integrate some data structures to help your collision detection. For instance, I just suggested in another thread the use of linked lists to limit the objects you must collision-detect against one another.
Ideas like yours might not always work, but your continual creative thinking will lead to ones that do. Sometimes you just have to try coding them to find out!
Hey, I'm currently trying to extract information from a 3d array, where each entry represents a coordinate in order to draw something out of it. The problem is that the array is ridiculously large (and there are several of them) meaning I can't actually draw all of it.
What I'm trying to accomplish then, is just to draw a representation of the outside coordinates, a shell of the array if you'd like. This array is not full, can have large empty spaces with only a few pixels set, or have large clusters of pixel data grouped together. I do not know what kind of shape to expect (could be a simple cube, or a complex concave mesh), and am struggling to come up with an algorithm to effectively extract the border. This array effectively stores a set of points in a 3d space.
I thought of creating 6 2d meshes (one for each side of the 3d array), and getting the shallowest point they can find for each position, and then drawing them separetly. As I said however, this 3d shape could be concave, which creates problems with this approach. Imagine a cone with a circle on top (said circle bigger than the cone's base). While the top and side meshes would get the correct depth info out of the shape, the bottom mesh would connect the base to the circle through vertical lines, making me effectivelly loose the conical shape.
Then I thought of annalysing the array slice by slice, and creating 2 meshes from the slice data. I believe this should work for any type of shape, however I'm struggling to find an algorithm which accuratly gives me the border info for each slice. Once again, if you just try to create height maps from the slices, you will run into problems if they have any concavities. I also throught of some sort of edge tracking algorithm, but the array does not provide continuous data, and there is almost certainly not a continuous edge along each slice.
I tried looking into volume rendering, as used in medical imaging and such, as it deals with similar problems to the one I have, but couldn't really find anything that I could use.
If anyone has any experience with this sort of problem, or any valuable input, could you please point me in the right direction.
P.S. I would prefer to get a closed representation of the shell, thus my earlier 2d mesh approach. However, an approach that simply gives me the shell points, without any connection between them, that would still be extremely helpful.
Thank you,
Ze
I would start by reviewing your data structure. As you observed, the array does not maintain any obvious spatial relationships between points. An octree is a pretty good representation for data like you described. Depending upon the complexity of you point set, you may be able to find the crust using just the octree - assuming you have some connectivity between near points.
Alternatively, you may then turn to more rigorous algorithms like raycasting or marching cubes.
Guess, it's a bit late by now to be truly useful to you, but for reference I'd say this is a perfect scenario for volumetric modeling (as you guessed yourself). As long as you know the bounding box of your point cloud, you can map these coordinates to a voxel space and increase the density (value) of each voxel for each data point. Once you have your volume fully defined, you can then use the Marching cubes algorithm to produce a 3D surface mesh for a given threshold value (iso value). That resulting surface doesn't need to be continuous, but will wrap all voxels with values > isovalue inside. The 2D equivalent are heatmaps... You can refine the surface quality by adjusting the iso threshold (higher means tighter) and voxel resolution.
Since you're using Java, you might like to take a look at my toxiclibs volumeutils library, which also comes with sevaral examples (for Processing) showing the general approach...
Imagine a cone with a circle on top
(said circle bigger than the cone's
base). While the top and side meshes
would get the correct depth info out
of the shape, the bottom mesh would
connect the base to the circle through
vertical lines, making me effectivelly
loose the conical shape.
Even an example as simple as this would be impossible to reconstruct manually, let alone algorithmically. The possibility of your data representing a cylinder with a cone shaped hole is as likely as the vertices representing a cone with a disk attached to the top.
I do not know what kind of shape to
expect (could be a simple cube...
Again, without further information on how the data was generated, 8 vertices arranged in the form of a cube might as well represent 2 crossed squares. If you knew that the data was generated by, for example, a rotating 3d scanner of some sort then that would at least be a start.