How to do gradient transitions using slimdx?

Question

I am making an image slide show using slimdx and c#. Till now I have done transitions using the matrix transformation but now I am trying to make transitions using some gray scale background image. Can any body please give me an idea how can i perform that or can post some code to give me an idea.

Answer 1

If we first consider the simple case of having two images that as a whole fades from one image in a seamless fashion into the other image, this would be cheapest to express as drawing a quad with a pixel shader.

This shader would have a float shader parameter you set from your code in the range of [0,1]. You can then bind and sample your two textures and lerp between them based on this constant factor.

A value of 0.0 would represent 100% of the first image, a value of 1.0 would be 100% of the second image, 0.25 would be a quarter of the first and three quarters of the second, and so on.

You can then use additional textures to alter the value of this interpolation parameter, like:

• you could a grayscale texture which could act as an offset to this parameter,
• you could use the parameter to index inside a 3D texture or a texture array which would represent your wipe,
• you could use the parameter to translate the texture coordinates used to sample a gradient texture, so that the static gradient band appears to move across your image.
• you could do something entirely else - with programmable shaders your imagination is the only limit (barring shader complexity limits from the shader model, of course).

Answer 2

Looking at the SlimDx documentation, I think more information could be useful like what classes you are using to diplay your images?

Generally for a fade-in/out transition you can use a quad with a texture or just a plain color, and using the 'tint' Color, you can make the quad more or less transparent.

If you are familiar with shaders, you can make a shader take multiple Textures and a float as input, and you can then easily calculate the needed mix.