GPU shader render precision about vamigaweb

[Vweber73]

I'm sure you will ! You're the man ! :)

[mithrendal]

@Vweber73

findings...

I have had a very precise picture in GPU renderer (like we see in software renderer) without the distortions seen in the picture above when the texture which is uploaded to the GPU has the same size as the display area i.e. narrow or standard ...

using an exact integer fraction of the shaders texture size also works e.g. texture has 720px width then 320px width display area is ok too but not 322px width ...

solution 1

whenever user changes display area or when borderless or viewport tracking changes display area automatically we may initialize a new texture buffer... currently one very big buffer is initially created and reused and the GPU scales the display area ... but not so precisly ...

solution 2

I bet my shader programming is not so good ... maybe when we use integers instead of floats here ?

vAmigaWeb/mainsdl.cpp

Lines 152 to 177 in 1024a74

	void set_texture_display_window(const GLuint program, float hstart, float hstop, float vstart, float vstop)
	{
	const float x1 = hstart / HPIXELS;
	const float x2 = hstop / HPIXELS;
	const float y1 = vstart / VPIXELS;
	const float y2 = vstop / VPIXELS;
	const GLfloat coords[] = {
	x1,y1, x2,y1, x1,y2, x2,y2
	};
	printf("%f %f %f %f\n",x1,x2,y1,y2);
	GLuint corBuffer;
	glGenBuffers(1, &corBuffer);
	glBindBuffer(GL_ARRAY_BUFFER, corBuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(coords), coords, GL_STATIC_DRAW);
	GLint corAttrib = glGetAttribLocation(program, "a_texcoord");
	glEnableVertexAttribArray(corAttrib);
	glVertexAttribPointer(corAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
	glUniform2f(glGetUniformLocation(merge, "u_diw_size"), hstop-hstart, vstop-vstart);
	printf("w=%f h=%f\n",hstop-hstart,vstop-vstart);
	}

[Vweber73]

Great findings ! But although I am proficient in C/C++/Java programming, I lack the video knowledge to help...

[mithrendal]

I am also not an gpu shader expert only understand the very basics… 😬but I am sure we will solve this, no?

[mithrendal]

some articles for reference which are describing our problem

https://colececil.io/blog/2017/scaling-pixel-art-without-destroying-it/
https://jorenjoestar.github.io/post/pixel_art_filtering/

[mithrendal]

more findings
when I use GL_LINEAR filtering then pixels are correct size for all display sizes but it gets blurry

maybe still better then current situation ?

[Vweber73]

Well... The ultimate goal is the real thing ! :)

[mithrendal]

fixed 😎

[Vweber73]

Congrats !!
Btw, restoring a snapshot does not restore anything in the parameters - not only the clock, but not the memory settings. Makes it a bit confusing...
Cheers

[mithrendal]

yes I know ... do you think we should reset the parameters in the settings dialog according to the loaded snapshot ? but then the loaded settings from the snapshot should not be persisted as default values, which are loaded on next cold start of vAmigaWeb right ?

[mithrendal]

could you make a new issue and describe the concept of how it should be to be less confusing ?

we close this now ok ? If something strange with GPU shader shows up we just reopen ...

[Vweber73]

Yes, just make them the parameters as long as the snapshot leaves, for consistency...
Cheers

[Vweber73]

Yes let's close this one.