Textures are used for the stones and the goban. The white stones are overlayed with an image for a slight grain effect. The goban will always have a wooden texture, switching this off getting an orange board makes little sense. The stone textures can be disabled, resulting in plain black and white stones. This will improve performance, but the overall quality drops significantly. Probably in future versions disabled textures might be removed. Textures don't hurt the performance much, and they add quite a lot to the overall scene.
The texture quality can be set to low and high. When zooming in, the difference should be obvious. Low quality textures will appear blocky. When running in hardware mode, high quality textures do not drop performance much, so it is a good idea to use them. However, when running in software mode high quality textures are a speed killer, so for software mode it is highly recommended to switch to low quality. When the board is not zoomed in closely, the difference is not too noticeable.
Light causes the reflection effect on the black stones, which look quite similar to the stones in the Java version of gGo. When rotating the board, the reflection will slider over the stone surface relatively to the light source, which is placed slightly to the upper left. Think about a lamp shining just over your head.
Shadows significantly add to the overall 3D scene. The shadows are drawn relative to the light source. Basically they are just another light effect, but can be toggled off independent from light to improve performance in software mode while keeping the reflection effect. Shadows require light to be enabled.
Blending is an important effect. All antialias effects (see below) depend on blending enabled. Blending means that the alpha value of each pixel will be calculated when drawing the scene. When you take the border of a stone or a grid line, the pixels close to the wooden board will have a lower alpha value, so the borderline will not appear blocky, instead the edge of the black grid lines or the stones will be smooth. When blending is disabled, all antialias effects will not work. Blending is a recommended feature, however it can be quite performance costly on software mode. You need to find out if trading the performance for quality is worth it. When running in hardware mode, blending is very fast and should be enabled.
You might notice the grid lines and stone edges can get blocky, which is called aliasing. The effect which prevents this is called antialiasing. glGo supports two antialias modes, a third is accessible via the configuration of your 3D driver.
Two simple but quite effective antialias settings affect the drawing of lines and stones only. This are the line and stone antialias settings in glGo. You find them in themenu. Blending must be enabled, else this will show little effect.
This will affect the grid on the goban and smooth the lines when rotating the board. If turned off, the lines will appear blocky. The quality of this effect depends on the capability of your graphic card.
This will affect the board of stones to appear smooth. The effect should be obvious when toggling this on and off. This is a recommended feature which does not affect performance much and even is fast in software mode, so there is little reason to turn this off.
Scene antialiasing will improve not only the lines and stones but the complete display. To enable this feature, turn on themenu item in glGo. You can configure if low or high quality should be used. This scene antialiasing effect can be very slow on older hardware. It only runs in hardware mode on very new cards (hardware supported accumulation buffer, to be specific), so this is quite slow when it is not supported by the card, as the CPU has to do the work. If you have a fast computer, on low quality setting it might still be performant enough. But with lots of stones on the board and on high quality settings this eats CPU power for breakfast unless your card has the above mentioned hardware accumulation buffer. I think Geforce4 has it, but not sure.
Modern graphic cards have a feature called Multisampling, which will also smooth the overall scene. glGo will automatically turn multisampling on if it is supported by the hardware.
You need to enable full screen antialiasing (FSAA) in your 3D driver. You can access this in the 3D driver configuration dialog, for NVidia cards (sorry, no idea about the ATI and Matrox drivers) there is a slider which allows the FSAA detail setting. On Linux you can control this feature by setting an environment variable, see the documentation of your driver. Unfortunately this configuration is not accessible from the application itself. FSAA is supported by most recent graphic cards.
You might need to play a little with the settings and your 3D driver configuration to find good settings which meet your needs for quality and performance.
On a medium to low-end computer you should be Ok if you have a recent 3D driver installed (see section requirements) and enable Blending, Line and Stone antialias, Textures and Light. Keep the Scene antialias in glGo disabled. If your card supports it, enable FSAA in the driver configuration. On a high-end computer give the glGo Scene antialiasing a try and see how much it drops the performance.
Render to texture means the full display is not instantly drawn on the window but instead first drawn into an image (a "texture") and then this texture is drawn on the window. The advantage of this feature is the display is buffered in the texture, and when you for example minimize and restore the window, redrawing the whole scene will be much faster as only the already existing texture is drawn again, not the whole scene again. Also when opening a menu or a dialog the cached texture will be used to redraw the window. Only when the board changes, like when a stone is played, the scene will be redrawn. This feature also prevents some display artifacts when other windows overlap the glGo board.
The disadvantage is a minimal performance drop as drawing the texture to the screen takes an extra step in the whole process, but this effect is minimal when running with hardware acceleration. Actually this feature will rather improve the overall performance as the scene does not need to be redrawn constantly when something happens to the window, like another window or dialog is laid over it. However, if you are running in software mode, disabling Render to texture will speed up glGo significantly.
When blurring is enabled, the whole scene will be slightly smeared. You maybe know this effect from common paint software, most offer a feature when you can smear the existing image with a brush.
Blurring only works if Render to texture is enabled. When the texture is drawn to the screen and blurring is enabled, it will be drawn several times having a small offset in each turn - this is called jittering. Each image will be blended into each other, and as each image has a faint offset to each other the whole scene will be slightly worn away. When Render to texture is disabled, this feature cannot work, as then the whole scene is only drawn once directly into the window. So enabling Blur while having Render to texture disabled makes no sense (yes, the software should check this, but it does not yet.)
I am currently not sure if blurring makes much sense. I personally don't like the effect much.
While rotating the board using the cursor keys, to be exact while one of the cursor keys is pressed down, some of the above mentioned display improvements are temporary disabled to speed up the rotating. While rotating the whole scene has to be redrawn quite often, so every unnecessary feature will slow this down. And while the picture is moving, not the best quality is required.
Once you release the key, the final scene will be drawn with all settings enabled again. This should make rotating more efficient while the quality drop should not be very noticeable during the movement. If you have a fast computer, you can probably keep this disabled. Try and see if this makes a significant performance difference.
The OpenGL scissor test allows to only draw a part of the whole scene instead of the complete view. The basic idea is: When adding just a single stone, usually done by playing it or navigating forward in a game review, and when there are no captures, then it is not really necassary to redraw the complete board with all stones just to add this one additional stone. This is especially true if there are quite a lot of stones, like more than 200, on the board, when rendering all stones is getting slow. In such a case the scissor test will prevent redrawing everything and only add the single new stone into the otherwise unchanged scene.
Obviously there are some problems with this concept. When there are captures, not only one stone has to be added but also other stones being removed. If there are SGF marks on the board they must be removed. When going through variations the ghost stones indicating branches need to be drawn or removed. In all these cases too much changes on the board so the scissor test makes no sense anymore. glGo will then automatically disable scissoring for such a move and redraw the full scene. When playing or moving through a normal game this is not much of a problem, as captures don't occur at every move, and when they occur scissoring is automatically disabled. However, when looking at a game with a lot of SGF markers, Kogos Joseki Dictionary being an extreme example, the scissor test makes no sense and should be completely disabled.
Besides being not trivial, scissoring will produce some display artifacts when the board is rotated. To sum it up, if you really need some speed improvement, try this feature for normal games and switch it off for SGF editing (or use the 2D board for this task). If your computer can handle the 3D board without scissoring properly, then keep it disabled. But on my old P2 with 333 MHz scissoring is a significant performance boost with more than 200 stones on the board.
Scissor test and render-to-texture both enabbled will create display distortion. Enable only one of these features at the same time.
Stone quality defines from how many triangles the wireframe of a stone is built. Using more triangles obviously looks better and is slower. High means a stone is created from 512 triangles, low means from 128 triangles. Why triangles instead of quads? Because most graphiccards can draw triangles much faster.
Any values above 512 don't improve the look anymore but get very slow, so "High" definately means good enough.
glGo supports a mark for the last move and a couple of common SGF marks like square, triangles, letters etc.
There are two markers available for the last move mark:
Simple marks appear very similar to the Java version. A plain circle is drawn on the stone - actually it is drawn inside the stone to avoid odd effects when rotating the board.
The SGF marks like square, triangle, circle and cross marks are always drawn as simple marks.
Multitextures are an extension to OpenGL and is only available when running in hardware mode. Most graphic cards should support multitextures. Multitextures means, a second texture can be laid over the stone. The white stones already have the grain texture, multitexture allows to add a second texture with a mark. This makes the marks look realistic, as if painted over the stone, and not floating above or inside the stone as the simple marks do. I intentionally made a mark texture which looks "as if painted", instead of the usual plain circle or cross. I think this looks pretty realistic. There is currently one problem with these marks, when zooming in closely and rotating, the marks slide over the stone. This has to be improved.
glGo will detect if your graphic card supports multitextures and enable this feature. If it is not supported, simple marks are automatically disabled.