annotate projects/tank_wars/vector_graphics.cpp @ 45:579c86316008 newapi

Major API overhaul. Moved to a single data structure for handling render functions. Functionally, generally similar except for scheduling within PRU loop function, which now uses interrupts from the PRU rather than polling. This requires an updated kernel.

/*
 * vector_graphics.cpp
 *
 *  Created on: Nov 10, 2014
 *      Author: parallels
 */

#include <cmath>

// Draw a line between two points at a specified rate in
// pixels per buffer sample. Indicate maximum available space.
// Returns space used
int renderLine(float x1, float y1, float x2, float y2, float speed,
			   float *buffer, int maxLength) {
	// Figure out length of line and therefore how many samples
	// are needed to represent it based on the speed (rounded to nearest int)
	float totalLineLength = sqrtf((x2 - x1)*(x2 - x1) + (y2 - y1)*(y2 - y1));
	int samplesNeeded = floorf(totalLineLength / speed + 0.5);

	// Now render into the buffer
	int length = 0;
	float scaleFactor = 1.0f / samplesNeeded;
	for(int n = 0; n < samplesNeeded; n++) {
		if(length >= maxLength - 1)
			return length;
		// X coordinate
		*buffer++ = x1 + (float)n * scaleFactor * (x2 - x1);
		// Y coordinate
		*buffer++ = y1 + (float)n * scaleFactor * (y2 - y1);
		length += 2;
	}

	return length;
}

// Draw an arc around a centre point at a specified rate of pixels
// per buffer sample. Indicate maximum available space.
// Returns space used
int renderArc(float x, float y, float radius, float thetaMin, float thetaMax,
			  float speed, float *buffer, int maxLength) {
	// Figure out circumference of arc and therefore how many samples
	// are needed to represent it based on the speed (rounded to nearest int)
	float circumference = (thetaMax - thetaMin) * radius;
	int samplesNeeded = floorf(circumference / speed + 0.5);

	// Now render into the buffer
	int length = 0;
	float scaleFactor = 1.0f / samplesNeeded;
	for(int n = 0; n < samplesNeeded; n++) {
		if(length >= maxLength - 1)
			return length;
		// Get current angle
		float theta = thetaMin + (float)n * scaleFactor * (thetaMax - thetaMin);

		// Convert polar to cartesian coordinates
		*buffer++ = x + radius * cosf(theta);
		*buffer++ = y + radius * sinf(theta);

		length += 2;
	}

	return length;
}

// Draw a single point for a specified number of frames
void renderPoint(float x, float y, float *buffer, float length) {
	while(length > 0) {
		*buffer++ = x;
		*buffer++ = y;
		length--;
	}
}