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King of Men

Member Since 16 Apr 2004
Offline Last Active Dec 23 2013 06:34 PM

Topics I've Started

Learning modern OpenGL

08 November 2013 - 04:04 PM

So I've been using OpenGL for a while and I feel I've got a reasonable grasp of the basics: Primitives, transforms, textures. I can make a sprite in a modelling program and get it up on the screen. But this is all using the fixed pipeline and basic glBegin, glEnd calls; I'd like to move on to the modern features. Can anyone recommend a good tutorial for understanding vertex shaders and such? For that matter, just a list of what the advanced features are would be helpful, so I know what the holes in my knowledge are. 

Seeking advice on presenting game information

08 October 2013 - 06:31 PM

I'm working on a turn-based, hex-based, 4X game. It is currently in a "playable" state, in that you can move armies around, recruit, attack, and there's a nod in the direction of supply lines. Much gameplay remains to be coded. Right now, though, I'm thinking of the interface. I've spent some time trying to reflect the game state in the main view, and am reasonably pleased with the engine, but the content needs a bit of work, and more to the point, input from someone who knows a bit about graphics. My screenshots, let me show you them:


This is a view of the main playing area, with an army selected - specifically, the one under the red banner. You can see the hex-line-vertex structure that forms the game surface, overlaid on green plains rising to a mountain in the center-right. If, like me, you know what's going on, you can also pick out villages, with their militia units and cows showing supply stockpiles, and the two castles. But none of this is very clear.


A different view of the playing area, offering perhaps some better idea of what's happening. Note the trees on the right.


A closeup on a village. At this distance the chimneys that distinguish the houses from being blobs of wood are visible. Note the militia on the left, armed with pitchforks.


A closeup on the cows, indicating that this village has a largish supply stockpile. Note also the fields among the trees, in the center; at the moment they are in the "fallow" state, but will change colour as the turns go and the village works them. Turns are a week long.


A closer view of the armies - distinct from the militias - showing the pikemen of the AI army, with their green banner, repeated on their uniform. In the background on the left, the archers and militia under the red banner of the human player; the archers get the banner on their uniform, the militia do not.

Now: I'm reasonably pleased with the way my graphics engine works, and with the sprites in a close view. What I'm not so happy about is how it all appears in an overview, ie zoomed out. Nothing stands out; you have to zoom in and fiddle with the view angle to extract any real information. So I'm open to suggestions. Could I have a better colour scheme? (The militia, especially, are a rather greyish blob at any sort of distance. Realistic-ish, but not very interesting.) Fiddle with the level of detail - abstract when zoomed out? (If so, I'd like to hear suggestions for how to present the same information: Size of the village, supply stockpile, size and unit type of the militia, and location/size/units of the field armies.) Something else?

Turing Machines

10 January 2011 - 09:33 PM

So there's something I don't understand about Busy Beaver numbers. Consider: We know that no Turing machine can calculate arbitrary BB numbers, because if one could, it could solve the Halting Problem. However, Turing machines are allowed to calculate particular BB numbers. Now, any Turing machine can emulate any other. So why can one not calculate any particular BB number by emulating a machine that can? Or have I just proved that there must exist at least one BB number which no Turing machine whatever can calculate?

Unexpected results with transparent textures

03 January 2011 - 06:12 PM

I am trying to draw some simple 2D graphics. My plan is to draw a quad in a single color, say green; then I draw a texture on top of that. The texture is mostly black, but partly transparent; thus I want the green to shine through the transparent parts, making an outline. It seems to me that this ought to happen when I use the GL_DECAL mode. In particular, where the texture is black and opaque, I should get color (1-1)*(0.0, 1.0, 0.0)+1*(0.0, 0.0, 0.0) = (0.0, 0.0, 0.0), which is black. Fine. But where the texture is transparent (and white), I should get (1-0)*(0.0, 1.0, 0.0)+0*(1.0, 1.0, 1.0)=(0.0, 1.0, 0.0), green. Instead, I get white, as shown in this screenshot:

Problem with decal mode

Clearly I'm misunderstanding something about how this works. Can anyone help me out?

This is my rendering code:

// Get coordinates
glColor4d(0.0, 1.0, 0.0, 1.0);
glBindTexture(GL_TEXTURE_2D, 0);
glVertex3d(coords11.first, coords11.second, -0.001);
glVertex3d(coords12.first, coords12.second, -0.001);
glVertex3d(coords21.first, coords21.second, -0.001);
glVertex3d(coords22.first, coords22.second, -0.001);
glColor4d(0.0, 0.0, 0.0, 0.0);

glBindTexture(GL_TEXTURE_2D, textureIDs[castleTextureIndices[i]]);
glTexCoord2d(0.0, 0.0); glVertex3d(coords11.first, coords11.second, 0.0);
glTexCoord2d(1.0, 0.0); glVertex3d(coords12.first, coords12.second, 0.0);
glTexCoord2d(1.0, 1.0); glVertex3d(coords21.first, coords21.second, 0.0);
glTexCoord2d(0.0, 1.0); glVertex3d(coords22.first, coords22.second, 0.0);

Gradient blending

10 October 2010 - 11:43 AM

I'm trying to draw hexes for a simple 2D game. I'd like to have different textures for different terrain in the hexes, and then blend the textures at the edges so as to create a smooth transition. It seems to me that this could be done by telling OpenGL to blend on a gradient, so that one end of a quad was fully one texture and the other end was fully the other, and a linear mix in between; but my Google-fu is not strong enough to tell me how this can be done. Can anyone point me to what I should look for? This seems like it ought to be a standard technique, so maybe I'm just missing the right keywords.

Alternatively, am I barking up the wrong tree and should use a different technique?