I'm writing some Java OpenGL code (though the principles are the same in C++ openGL). I have a situation where I want to render certain items on top of others. I can do that by disable the depth test or by setting it to GL_ALWAYS) for those items and that works well. The issue is that colors of those items on top seem to be darkened by the items underneath it. I'm not sure if it's a lighting issue or if it's some blending issue but I'm trying to show the item's color without being affected by the colors around it, regardless of this item's z-position (since depth testing is set to ALWAYS). Is there a lighting setting or blending setting I should be using for this?
thanks,
Jeff
I think in this situation, I'd leave the depth settings alone, but adjust the Z value of the objects based on the drawing order (for those items you want drawn based on order instead of normal depth).
glBegin(GL_WHATEVER);
for (int i=0; i<num_objects; i++)
glVertex(object[i].x, object[i].y, i/-100.0f);
glEnd(GL_WHATEVER);
Related
I have many problems unsolved, and i'm kind of new at LWJGL.
Here is a screen: http://image.noelshack.com/fichiers/2015/07/1423885261-sans-titre.png
(this is 20x20x20 simple cube)
But as you can see, my fps are not bigger than 40 and every face of the cube is showing. How can i fix the fps drop and hide the hidden block behind another one ?
I have glEnable(GL_DEPTH_TEST); and glEnable(GL_CULL_FACE); but it only work INSIDE the block :x ...
Sorry for my english too but i really need help :p
Culling
If culling only works if you are inside a block your vertex winding order is most likely mixed up. If so you might want to change it from the default GL_CCW to GL_CW or fix your vertex order to the default. Reference here
SpeedUp
For this your question has too few information. If you are not doing so already you might want to switch to using Vertex_Buffer_Object. Preferably using a single geometry that is only translated.
An additional approach would be to only render objects that are in line of sight of the camera. One method for this is a Binary Search Tree
(Sorry in advance, I'm not at my computer so I can't provide code)
I have a voxel based game, and I wanted to add in transparent textures, namely glass. I realized that transparent textures would throw things off (looking through other blocks), so I used my shaders to remove any alpha components lower than the alpha value of the glass texture. Currently, the glass has an alpha of 0.26 (coordinates range from 0 - 1), and it works fine. But, if I want to add some transparency to the glass instead of removing all transparency, I run into my old issue where you can see through the blocks behind the glass.
I read in a few places that I would need to sort my geometry from front to back. Does this still pertain to my situation even after using shaders? I use display lists, for each chunk in my world, should I keep two lists, one for opaque blocks and one for transparent? So when I render, I would do one pass and render the opaque lists, and then do another render pass, and render the chunks inversely and render the transparent list?
Or is there a better way to do this?
looking through blocks behind transparent geometry means you still have depth checking enabled meaning the blocks behind the glass didn't get rendered.
I read in a few places that I would need to sort my geometry from
front to back. Does this still pertain to my situation even after
using shaders?
yes you still need to sort, geometry shaders don't solve that issue
however you only need to sort the transparent geometry when you render them after the opaque geometry (after turning on alpha blending)
Is it possible to change the edge shape in JUNG? For example, I would like to have the edge change it's color gradually in a way similar to a progress bar. What about the edge label font size?
Thanks.
Yes, sort of... Also - I'm not sure which version of JUNG you're using, but this works in the latest JUNG 2 release (I realize JUNG 3 might be under development currently, but last time I checked, it wasn't stable enough to be used for production-level code).
1. Labelling: First, you need to implement the Transformer<EdgeType,Font> interface that converts your edge instances into Font instances. Then call [VisualizationViewer instance].getRenderContext().setEdgeFontTransformer([Transformer<EdgeType,Font> instance]).
2. Color/Stroke Customization: This is a little trickier, because the only way you can have this change color gradually (that I am aware of) is by creating a Transformer<EdgeType,Paint> that returns different paints for edge type instances over time. There are several transformers used for edges - these control the draw, the fill, and the Stroke, and have similar method names like the one mentioned for the labeller in step 1. You will either need to control when the graph panel repaints manually or ensure that JUNG's animation renderer is turned on so that repaints happen continuously.
I am attempting to create a "hole in the fog" effect. I have a background grid image, overlapped onto that I have a "fog" texture that I use to show that certain areas are not in view. I am attempting to cut a chunk out of "fog" that will show the area that is currently in view. I am trying to "mask" a part of the fog off the screen.
I made some images to help explain what I am after:
Background:
"Mask Image" (The full transparency has to be on the inside and not the outer rim for what I am going to use it for):
Fog (Sorry, hard to see.. Mostly Transparent):
What I want as a final Product:
I have tried:
Stencil-Buffer: I got this fully working except for one fact... I wasn't able to figure out how to retain the fading transparency of the "mask" image.
glBlendFunc: I have tried many different version of the parameters and many other methods with it (glColorMask, glBlendEquation, glBlendFuncSeparate) I started by using some parameter that I found on this website: here. I used the "glBlendFunc(GL_ZERO, GL_ONE_MINUS_SRC_ALPHA);" as this seemed to be what I was looking for but... This is what ended up happening as a result: (Its hard to tell what is happening here but... There is fog covering the grid in the background. Though, the mask is just ending up as an fully opaque black blob when its supposed to be a transparent part in the fog.
Some previous code:
glEnable(GL_BLEND); // This is not really called here... It is called on the init function of the program as it is needed all the way through the rendering cycle.
renderFogTexture(delta, 0.55f); // This renders the fog texture over the background the 0.55f is the transparency of the image.
glBlendFunc(GL_ZERO, GL11.GL_ONE_MINUS_SRC_ALPHA); // This is the one I tried from one of the many website I have been to today.
renderFogCircles(delta); // This just draws one (or more) of the mask images to remove the fog in key places.
(I would have posted more code but after I tried many things I started removing some old code as it was getting very cluttered (I "backed them up" in block comments))
This is doable, provided that you're not doing anything with the alpha of the framebuffer currently.
Step 1: Make sure that the alpha of the framebuffer is cleared to zero. So your glClearColor call needs to set the alpha to zero. Then call glClear as normal.
Step 2: Draw the mask image before you draw the "fog". As Tim said, once you blend with your fog, you can't undo that. So you need the mask data there first.
However, you also need to render the mask specially. You only want the mask to modify the framebuffer's alpha. You don't want it to mess with the RGB color. To do that, use this function: glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_TRUE). This turns off writes to the RGB part of the color; thus, only the alpha will be modified.
Your mask texture seems to have zero where it is visible and one where it isn't. However, the algorithm needs the opposite, so you should either fix your texture or use a glTexEnv mode that will effectively flip the alpha.
After this step, your framebuffer should have an alpha of 0 where we want to see the fog, and an alpha of 1 where we don't.
Also, don't forget to undo the glColorMask call after rendering the mask. You need to get those colors back.
Step 3: Render the fog. That's easy enough; to make the masking work, you need a special blend mode. Like this one:
glEnable(GL_BLEND);
glBlendEquation(GL_FUNC_ADD);
glBlendFuncSeparate(GL_ONE_MINUS_DST_ALPHA, GL_DST_ALPHA, GL_ZERO, GL_ONE);
The separation between the RGB and A blend portions is important. You don't want to change the framebuffer's alpha (just in case you want to render more than one layer of fog).
And you're done.
The approach you're currently taking will not work, as once you draw the fog over the whole screen, there's no way to 'erase' it.
If you're using fixed pipeline:
You can use multitexturing (glTexEnv) with fixed pipeline to combine the fog and circle textures in a single pass. This function is probably kind of confusing if you haven't used it before, you'll probably have to spend some time studying the man page. You'll do something like bind fog to glActiveTexture 0, and mask to glActiveTexture 1, enable multitexturing, and then combine them with glTexEnv. I don't remember exactly the right parameters for this.
If you're using shaders:
Use a multitexturing shader where you multiply the fog alpha with the circle texture (to zero out the alpha in the circle region), and then blend this combined texture into the background in a single pass. This is probably a more conceptually easy approach, but not sure if you're using shaders.
I'm not sure there's a way you can do this where you draw the fog and the mask in separate passes, as they both have their own alpha values, it will be difficult to combine them to get the right color result.
I am trying to draw some bar graphs with a data set that contains overlapping priorities.
E.g. three bars of different colors may be drawn at one point, but the one with the highest priority will be shown. This works most of the time, but I am getting some artifacts on my plot as some of the colors from lower priorities leak through occasionally. Any ideas of where I can look to fix this problem?
I thought it may have been an anti-aliasing issue, but turning it on or disabling it has no effect on the artifacts.
When I've seen things like this before it was because I was graphing multiple data series, and for the most part there was a huge overlap in the datasets and only the last dataset rendered (top one) was visible most of the time. I suspect that whatever you are doing in your hide code might not be working as well as you think and the 'bleeding' of the other colours is the datasets where the overlap is less significant. Try an experiment and change the order in which your datasets are rendered - I'll bet that you see suddently that the predominant colours of your bars change.
I'm not quite sure what you mean, but you probably should remove the priorities you don't want to see from the data model altogether, then they won't be painted at all.