Can anyone suggest why my low opacity painting does this weird blending, while the SketchBookX app does it perfect?
In both images attached the vertical strokes on the left are done at full opacity, the strokes on the right are done at low opacity. The top image is mine and as you can see the strokes on the right at low opacity turn a orange-red color and don't blend/mesh with the full opacity strokes. But the SketchBookX app blends perfectly and maintains the same color.
I'm using glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA) and have tried many variations with no luck, so I'm starting to think there are other things that are giving me this problem.
Do I need to handle this problem in the fragment shader? I currently have this,gl_FragColor = color * rotatedTexture; I'm using PNGs for brush textures.
UPDATE: Im getting the same results without using a texture. gl_FragColor = color;
I want it to be like mixing ink, not like mixing light :)
Related
What GLBlendFunc would solve this problem?
I am currently using:
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
I want the paint app to act like real paint would, but it seems that when using a lower opacity color, it won't paint over a solid white color.
Here is my example
What I am expecting is that in Step 3 the light pink paint would still paint lightly over the previous white strokes even though the opacity is at 0.1 not 1.0
I would like it to behave other paint app. These example is from Photoshop.
I have been working with OpenGL in iOS, and setting the colors with glColor4f(r,g,b,a) and then drawing my own color on a white UIImageView. I basically have a brush, which is then moved around my user's touch, and then it paints the color onto the canvas. But this color needs to be water paint (like smudged color)
Does anyone understand/knows how to get a water color like this app does, and how the background UIImageView has a texture on it?
https://itunes.apple.com/us/app/hello-watercolor/id539414526?mt=8
or checkout water paint in this. http://www.fiftythree.com/paper
I created a bounty on this as I am really having a hard time to grasp how to derive such smooth flowing colors out of the normal colors. Even if you guys point me in the right direction, or to some sample code on how I can get the effect of water-paint, it would be really helpful ^_^
And as a bonus, it would be also be helpful if you can point out to me how to get canvas on which it is painted on looks realistic, and blended with the paint? Does Blending/GLSL have to do with any of this?
Is there any sample project on this?
If you are still struggling with the basics of getting realistic looking water colors working, you may want to experiment/prototype in photoshop first.
http://www.zoepiel.com/tutorials/watercolor/ shows some very effective tricks for creating watercolor images with simple tools.
The most interesting one is to multiply a group of watercolor layers with a greyscale watercolor paper image. The texture of the paper makes some parts remain white, and other parts saturate with color, just like real watercolor.
Each layer remains 'wet' in the sense that the colors within it blend, but the layers are 'dry' with respect to each other.
She also explains some of her brush and blur settings and shows what they do.
Once you can produce the desired effect in photoshop, you'll have clear specifications of what you want to do and you'll be quite a bit closer to programming it out.
Looking at the examples you posted, it looks like they are using a simple Gaussian Blur with a radius of double your brush size. This may be an incomplete solution, but it's at least the first level.
I have been working with OpenGL in iOS, and setting the colors with glColor4f(r,g,b,a) and then drawing my own color on a white UIImageView. I basically have a brush, which is then moved around my user's touch, and then it paints the color onto the canvas. But this color needs to be water paint (like smudged color)
Does anyone understand/knows how to get a water color like this app does, and how the background UIImageView has a texture on it?
https://itunes.apple.com/us/app/hello-watercolor/id539414526?mt=8
or checkout water paint in this. http://www.fiftythree.com/paper
I created a bounty on this as I am really having a hard time to grasp how to derive such smooth flowing colors out of the normal colors. Even if you guys point me in the right direction, or to some sample code on how I can get the effect of water-paint, it would be really helpful ^_^
And as a bonus, it would be also be helpful if you can point out to me how to get canvas on which it is painted on looks realistic, and blended with the paint? Does Blending/GLSL have to do with any of this?
Is there any sample project on this?
If you are still struggling with the basics of getting realistic looking water colors working, you may want to experiment/prototype in photoshop first.
http://www.zoepiel.com/tutorials/watercolor/ shows some very effective tricks for creating watercolor images with simple tools.
The most interesting one is to multiply a group of watercolor layers with a greyscale watercolor paper image. The texture of the paper makes some parts remain white, and other parts saturate with color, just like real watercolor.
Each layer remains 'wet' in the sense that the colors within it blend, but the layers are 'dry' with respect to each other.
She also explains some of her brush and blur settings and shows what they do.
Once you can produce the desired effect in photoshop, you'll have clear specifications of what you want to do and you'll be quite a bit closer to programming it out.
Looking at the examples you posted, it looks like they are using a simple Gaussian Blur with a radius of double your brush size. This may be an incomplete solution, but it's at least the first level.
I've been using XNA for awhile now and I really enjoy using its interface. Right now we're trying to make a "fog of war" system. We're making an RTS and we're basically trying to obscure the map. Units on the map have influence, and show what's happening. They reveal a specific area on the map. Previously we used a tile based interface but we weren't happy with the appearance. Instead, we decided to draw a black mask on the screen, then reveal a transparent circle with DrawUserPrimitives. Here's the problem: When we draw a black mask on the screen, followed by the transparent circle, the screen is entirely black. Reversing the order doesn't change anything either. We've also tried every SpriteBatch BlendState we can find.
OUR CURRENT METHOD:
Right now, we're drawing a full black texture onto the screen, then drawing a transparent circle. The result is an entirely black screen.
OUR DESIRED OUTCOME:
Drawing the circle will reveal a section of the screen, but keep the rest obscured. We'd be able to draw multiple circles, all with their own radius, that would could be near each other without causing problems.
Basically, we're trying to draw a black mask, but reveal portions of the screen. We can't just make a circle texture and make the edges transparent, because we're trying to make the center of the circle transparent. We can't make the center transparent, because then when two such textures were near each other, their borders would show up. How would I go about making the mask, then revealing sections of it?
Regards
Ares
You could render the graphics normally to one render target, then paint the visible area in white on a black background in another render target, then render the second into the first with the Min BlendFunction.
Alternately, using only one render target, draw the graphics normally, then clear the alpha channel (by painting a rectangle over the whole screen with ColorWriteChannels = Alpha and alpha blend factors both 0), then draw the visible area with ColorWriteChannels = Alpha only.
I'm just starting game development and I thought a game like Tank wars or Worms would be nice.
The hardest part I can think of so far is making the terrain destructible and I want to know how it's done before doing the easy parts.
I thought that explosion could have a mask texture which could be scaled for different weapons. Then using that mask I should make underlying terrain transparent (and optionally draw a dark border).
(source: mikakolari.fi)
How do I achieve that?
Do I have to change the alpha value pixel by pixel or can I use some kind of masking technique? Drawing a blue circle on top of the terrain isn't an option.
I have versions 3.1 and 4.0 of XNA.
This tutorial is what you are searching:
http://www.riemers.net/eng/Tutorials/XNA/Csharp/series2d.php
Capter 20: Adding explosion craters
In short:
You have 2 textures: 1 Color Texture (visible), 1 Collision Texture (invisible)
You substract the explosion image from your collision texture.
To get the dark border: expand the explosion texture and darken the color in this area.
Now you generate a new Color Texture (old color - collison = new color).
This is a difficult question to answer - because there are many ways you could do it. And there are pros and cons to each method. I'll just give an overview:
As an overall design, you need to keep track of: the original texture, the "darkness" applied, and the "transparency" applied. One thing I can say almost for sure is you want to "accumulate" the results of the explosions somewhere - what you don't want to be doing is maintaining a list of all explosions that have ever happened.
So you have surfaces for texture, darkness and transparency. You could probably merge darkness and transparency into a single surface with a single channel that stores "normal", "dark" (or a level of darkness) and "transparent".
Because you probably don't want the dark rings to get progressively darker where they intersect, when you apply an explosion to your darkness layer with the max function (Math.Max in C#).
To produce your final texture you could just write from the darkness/transparency texture to your original texture or a copy of it (you only need to update the area that each explosion touches).
Or you could use a pixel shader to combine them - the details of which are beyond the scope of this question. (Also a pixel shader won't work on XNA 4.0 on Windows Phone 7.)
You should Make a new Texure2D with the Color of desired pixels.Alpha = 0.
Color[] bits = new Color[Texture.Width * Texture.Height];
Texture.GetData(bits);
foreach(Vector2D pixel in overlapedArea)
{
int x = (int)(pixel.X);
int y = (int)(pixel.Y);
bits[x + y * texture.Width] = Color.FromNonPremultiplied(0,0,0,0));
}
Texture2D newTexture = new Texture2D(texture.GraphicsDevice, texture.Width, texture.Height);
newTexture.SetData(bits);
Now replace the new Texture2D with the Last Texture and you're good to go!
For more code about Collision, or changing texture pixels color go to this page for codes:
http://www.codeproject.com/Articles/328894/XNA-Sprite-Class-with-useful-methods