Chowdren: Fast Construct runtime for consoles/desktop

NetOne

It's an interesting idea, but if Chowdren were an official product, people would also assume full and official support for their games. Right now, Chowdren is extended whenever a game we are porting requires it, and that has worked well for us. It allows us to get real games running on Chowdren and to produce real results, and it is clear how our work will be funded.

For now, Chowdren will remain its own runtime. However, I will try to keep Scirra in the loop about Chowdren, in case there is something to learn from the Chowdren approach and vice-versa.

In related news, our port of Iconoclasts (made in Construct 1) is releasing on Nintendo Switch on August 2!

I hope we can announce some of the Construct 2 games we are working on soon as well.

elliot

For now, I won't make benchmarks available here. You can contact me by mail or on the Discord server if you'd like more info.

In general, Chowdren is significantly faster than the standard runtimes. However, making specific numbers available would undermine the fact that the standard runtimes are viable for the majority of users. Ashley & team are doing a great job of identifying performance hotspots, as can be seen in their work on the expression compiler.

Cryptwalker

You can send me your project on e.g. the Discord server. Hopefully, I'll have time to take a look soon!

I have some news: Chowdren can now automatically merge effects together. This means that most of the time, Chowdren does not need an intermediate framebuffer to render objects with effects, which the standard runtime will have to do in many cases. If you use a lot of effects, you can expect this to yield some large performance gains.

With the effects merging feature, there is also support for most Construct effects now.

Technical details

Consider two GLSL fragment shaders as follows:

// shader 1, constant multiply
void main() {
 gl_FragColor = texture2D(texture, texture_coordinate);
 gl_FragColor.rgb *= 2.0;
}

// shader 2, monochrome
void main() {
 vec4 col = texture2D(texture, texture_coordinate);
 col *= vec4(0.299, 0.587, 0.114, 1.0);
 col.rgb = vec3(col.r+col.g+col.b);
 gl_FragColor = col;
}

vec4 temp_color_1;
vec2 temp_coord_1;

void main_1() {
 temp_color_1 = texture2D(texture, temp_coord_1);
 temp_color_1 *= 2.0;
}

vec4 sample_1(vec2 tc)
{ temp_coord_1 = tc; main_1(); return temp_color_1; }

void main_2() {
 vec4 col = sample_1(texture_coordinate);
 col *= vec4(0.299, 0.587, 0.114, 1.0);
 col.rgb = vec3(col.r+col.g+col.b);
 gl_FragColor = col;
}

void main() { main_2(); }

void main ()
{
 vec4 col_1;
 col_1 = vec4(0.598, 1.174, 0.228, 2.0) *
 texture2D(texture, texture_coordinate);
 col_1.xyz = vec3(col_1.x + col_1.y + col_1.z);
 gl_FragColor = col_1;
}

Another update: on some platforms, we can get rid of temporary framebuffers entirely for effects that do not use cross-sampling. Most effects do not use cross-sampling, so this significantly improves the performance of effects, especially popular ones like Overlay and Screen.

This is achieved by using memory barriers on platforms that support it (such as console platforms, and Direct3D 11/OpenGL with glTextureBarrier). This allows us to read a texture while writing to it at the same time, so a temporary framebuffer isn't necessary. WebGL does not support memory barriers, which may be a reason why the regular Construct runtimes do not perform this optimization.

As described in the effect compositor writeup from Ashley, objects sometime require predrawing in the standard runtimes, such as when objects are rotated. By using the right texture coordinates for the background texture, we can also skip this step, removing another case where temporary framebuffers are used.

In Chowdren, there are now only a few situations where a temporary framebuffer is required:

• When a layer has 'force own texture', is not fully opaque, or uses an effect, a temporary framebuffer is needed to render the intermediate result.
• When an object uses a cross-sampling effect (such as WarpMask, WaterBg), a partial copy of the background is made.

Headbang Games

Please check your inbox :)