Is it possible to render a coloured texture in black and white using ES 1.X? If yes, how?
The only thing I can think of is very convoluted — using the GL_COMBINE texEnv mode to do a per-pixel dot product, though I can't seem to find a route through that doesn't involve an intermediate FBO and reducing the precision of your RGB channels to 7 bits a piece. So you're using the dot3 functionality that's generally intended for lighting, but because you don't want to use negative values you're ending up with half the available range. You'd basically just dot product everything with the vector (0.299, 0.587, 0.114) and output that on all three channels.
With a fragment shader that converts the color information into grayscale. Its pretty simple, just add all three channels and divide them with three (there are more advanced ways but this simple way works in most if not all cases).
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I'm making a simple 3D game using my own shader, and want to emulate an 8-bit pixel art style. To do this, I need to sample a low-resolution texture without the sampler interpolating between inter-pixel values. Hopefully this will also reduce processing time since it won't need to calculate the interpolation. Is there a way I can accomplish this?
Ok, turns out there was something I didn't realise about 2D textures. I'd already set its Filter Mode to 'point', which turns off interpolation in the sampling, but I hadn't noticed that there's a box marked 'Non-Power of 2'. What this does is, if your texture has dimensions that aren't a power of 2 (i.e. 1024) it upscales it so that it is. It does this so that it can apply compression to the texture, since compression only works on power-of-2 images in Unity. However, it applies antialiasing to the upscale regardless of Sample Mode, so the interpolation was actually being 'baked in' by the compiler and had nothing to do with the sampler or the shader whatsoever.
Turning this OFF solved the problem; however once I'm happy with my textures I will be expanding them to a power-of-2 size with trailing padding in order to take advantage of it.
I have seen many tutorials that people blend two images that are placed on top of each other very nicely in Photoshop. For example here are two images that are placed on top of each other:
Then in Photoshop after some work, the edges (around the smaller image) will be erased and two images are nicely mixed.
For example, this is a possible end result:
As it can be seen there is no edge and two images are very nicely blended, without blurring.
Can someone point me to any article or post that shows the math behind it? If there is a MATLAB code that can do it, that would be even better. Or at least if someone can tell me what is the correct term for this so I can do Google search on the topic.
Straight alpha blending alone is not sufficient, as it will perform a uniform mixing of the two images.
To achieve nice-looking results, you will need to define an alpha map, i.e. an image of the same size where you adjust the degree of transparency depending on the image that should dominate.
To obtain the mask, you can draw it by hand, for example as a filled outline, as a path or a polygon. Then you have to strongly blur this mask to get a smooth blend.
It looks very difficult (if not impossible) to automate this, as no software can guess what you want to enhance.
The term you are looking for is alpha blending.
https://en.wikipedia.org/wiki/Alpha_compositing#Alpha_blending
The maths behind it boils down to some alpha weighted sums.
Matlab provides the function imfuse to achieve this:
https://de.mathworks.com/help/images/ref/imfuse.html
Edit: (as it still seems to be unclear)
Let's say you have 2 images A and B wich you want to blend.
You put one image over the other so for each coordinate you have 2 RGB touples.
Now you need to define the weight of both images. Will you only see the colour of image A or B or which ratio will you choose to mix them?
This is done by alpha values.
So all you need is a 2d function that defines the mixing ratio for each pixel.
Usually you have values between 0 and 1 where 0 shows one image, 1 shows the other image, 0.5 will mix them both equally and so on...
Just read the article I have linked. It gives you a clear mathematical definition. I can't provide more detail than that.
If you have problems understanding that I urge you to read a book on image processing fundamentals.
I'm looking for a way to dynamically change a part of a Quad that has a SpriteRenderer attached to it. Let's say I have a red Quad and a blue Quad, and then I drag one onto the other (fast or slow), the intersecting part should be colored using a green sprite. This illustration shows the scenario I'm trying to solve.
Can someone please help me with this?
You have two options:
First, if your mid color will be the correct mixture of other two color, in this case it would be yellow, you can use Mobile Particle/Additive or Mobile Particle/Multiply Shaders.
In a second way, you can write your own shader that takes the intersection area as parameter and paint your textures according to parameters.
I want to use bitmap images as a "map" for levels in iphone game. Basicly it's all about the location of obstacles in the rectangular world. The obstacles would be color-coded -- where the white pixel is, there's no obstacle. Black means there is one at this point.
Now I need to use this data to do 2 things: (a) display the level map, (b) for in-game calculations. So, in general, I need a way to read the data from the bitmap and create some data structure (matrix-like) with those information - to both overlay the bitmap onto the level graphics as well as to calculate collisions and such.
How should I do it? Is there any easy way to read the data from image? And what's the best format to keep the images for this?
Have you looked at how Texture2D translates an image file to an OpenGL Texture ?
Tip: take a look at this Method in Texture2D.m:
- (id) initWithCGImage:(CGImageRef)image orientation:(UIImageOrientation)orientation sizeToFit:(BOOL)sizeToFit pixelFormat:(Texture2DPixelFormat)pixelFormat filter:(GLenum) filter
In 3D apps, it's quite common to use this kind of representation for height maps, in a height map, you use a Texture with colors that range from black to white ( white represents the maximum altitude )
For example, from this:
To this:
That was just to tell you that your representation is not that crazy :).
About reading the bitmap, I would also recommend you to read this (just in case you want to go deeper)
Hope I helped a bit!
I've tried using pngs with gradients as textures in my OpenGL ES based iPhone game. The gradients are not drawn correctly. How can I fix this?
By "not drawn correctly" I mean the gradients are not smooth and seem to degrade to sections of a particular color rather a smooth transition.
The basic problem is having too few bits of RGB in your texture or (less likely) your frame buffer. The PNG file won't be used directly by the graphics hardware -- it must be converted into some internal format. I do not know the OpenGL ES API, but presumably you either hand it the .PNG file directly or you first do some kind of conversion step and hand the converted data to Open GL ES. In either case consult the relevant documentation to ensure that the internal format used is of sufficient depth. For example, a 256 color palettized image will be sufficient as would a 24 bit RGB or 32 bit RGBA format. I strongly suspect your PNG is converted to RGB15 or RGB16 which has only 5 or 6 bits per color component -- not nearly enough to display a smooth gradient.